Jane Skok, Ph.D.

RUNX Transcription Factor-Mediated Association of Cd4 and Cd8 Enables Coordinate Gene Regulation
Collins, Amelie; Hewitt, Susannah L; Chaumeil, Julie; Sellars, Maclean; Micsinai, Mariann; Allinne, Jeanne; Parisi, Fabio; Nora, Elphege P; Bolland, Dan J; Corcoran, Anne E; Kluger, Yuval; Bosselut, Remy; Ellmeier, Wilfried; Chong, Mark M W; Littman, Dan R; Skok, Jane A
2011 Mar 25;34(3):303-314, Immunity
T cell fate is associated with mutually exclusive expression of CD4 or CD8 in helper and cytotoxic T cells, respectively. How expression of one locus is temporally coordinated with repression of the other has been a long-standing enigma, though we know RUNX transcription factors activate the Cd8 locus, silence the Cd4 locus, and repress the Zbtb7b locus (encoding the transcription factor ThPOK), which is required for CD4 expression. Here we found that nuclear organization was altered by interplay among members of this transcription factor circuitry: RUNX binding mediated association of Cd4 and Cd8 whereas ThPOK binding kept the loci apart. Moreover, targeted deletions within Cd4 modulated CD8 expression and pericentromeric repositioning of Cd8. Communication between Cd4 and Cd8 thus appears to enable long-range epigenetic regulation to ensure that expression of one excludes the other in mature CD4 or CD8 single-positive (SP) cells
— id: 129323, year: 2011, vol: 34, page: 303, stat: Journal Article,

The RAG2 C terminus suppresses genomic instability and lymphomagenesis
Deriano, Ludovic; Chaumeil, Julie; Coussens, Marc; Multani, Asha; Chou, YiFan; Alekseyenko, Alexander V; Chang, Sandy; Skok, Jane A; Roth, David B
2011 Mar 3;471(7336):119-123, Nature
Misrepair of DNA double-strand breaks produced by the V(D)J recombinase (the RAG1/RAG2 proteins) at immunoglobulin (Ig) and T cell receptor (Tcr) loci has been implicated in pathogenesis of lymphoid malignancies in humans and in mice. Defects in DNA damage response factors such as ataxia telangiectasia mutated (ATM) protein and combined deficiencies in classical non-homologous end joining and p53 predispose to RAG-initiated genomic rearrangements and lymphomagenesis. Although we showed previously that RAG1/RAG2 shepherd the broken DNA ends to classical non-homologous end joining for proper repair, roles for the RAG proteins in preserving genomic stability remain poorly defined. Here we show that the RAG2 carboxy (C) terminus, although dispensable for recombination, is critical for maintaining genomic stability. Thymocytes from 'core' Rag2 homozygotes (Rag2(c/c) mice) show dramatic disruption of Tcralpha/delta locus integrity. Furthermore, all Rag2(c/c) p53(-/-) mice, unlike Rag1(c/c) p53(-/-) and p53(-/-) animals, rapidly develop thymic lymphomas bearing complex chromosomal translocations, amplifications and deletions involving the Tcralpha/delta and Igh loci. We also find these features in lymphomas from Atm(-/-) mice. We show that, like ATM-deficiency, core RAG2 severely destabilizes the RAG post-cleavage complex. These results reveal a novel genome guardian role for RAG2 and suggest that similar 'end release/end persistence' mechanisms underlie genomic instability and lymphomagenesis in Rag2(c/c) p53(-/-) and Atm(-/-) mice
— id: 128877, year: 2011, vol: 471, page: 119, stat: Journal Article,

A multifunctional element in the mouse Igkappa locus that specifies repertoire and Ig loci subnuclear location
Xiang, Yougui; Zhou, Xiaorong; Hewitt, Susannah L; Skok, Jane A; Garrard, William T
2011 May 1;186(9):5356-5366, Journal of immunology
Nonbiased V gene usage for V(D)J joining is essential for providing an optimal immune system, but no cis-acting sequence with this function has been uncovered. We previously identified a recombination silencer and heterochromatin targeting element in the Vkappa-Jkappa intervening sequence of germline Igkappa transgenes, which we termed Sis. We now have generated Sis knockout mice in the endogenous locus. Intriguingly, Sis(-/-) mice exhibit a skewed Igkappa repertoire with markedly decreased distal and enhanced proximal Vkappa gene usage for primary rearrangement, which is associated with reduced occupancy of Ikaros and CCCTC-binding factor in the Vkappa-Jkappa intervening sequence in pre-B cells, proteins believed to be responsible for dampening the recombination of nearby Vkappa genes and altering higher-order chromatin looping. Furthermore, monoallelic heterochromatin localization is significantly reduced in Sis(-/-) mice for Igkappa in cis and IgH loci in trans in pre-B cells. Because Sis(-/-) mice still allelically excluded Igkappa and IgH loci and still exhibited IgL isotype exclusion, we concluded that stable localization at pericentromeric heterochromatin is neither necessary nor sufficient for the establishment or maintenance of allelic exclusion. Hence, Sis is a novel multifunctional element that specifies repertoire and heterochromatin localization to Ig genes
— id: 133891, year: 2011, vol: 186, page: 5356, stat: Journal Article,

It takes two: Communication between homologous alleles preserves genomic stability during V(D)J recombination
Brandt, Vicky L; Hewitt, Susannah L; Skok, Jane A
2010 Jan;1(1):23-29, Nucleus (Austin, Tex.)
Chromosome pairing is involved in X chromosome inactivation, a classic instance of monoallelic gene expression. Antigen receptor genes are also monoallelically expressed ('allelically excluded') by B and T lymphocytes, and we asked whether pairing contributed to the regulation of V(D)J recombination at these loci. We found that homologous immunoglobulin (Ig) alleles pair up during recombination. Homologous Ig pairing is substantially reduced in the absence of the RAG1/RAG2 recombinase, but a transgene expressing an active site RAG1 mutant (which binds but does not cleave DNA) rescues pairing in Rag1(-/-) developing B cells. RAG-mediated cleavage on one allele induces the other allele to relocate to pericentromeric heterochromatin (PCH), likely to ensure that only one allele is cut at a time. This relocation to PCH requires the DNA damage sensor ATM (ataxia telengiectasia mutated). In the absence of ATM, repositioning at PCH is diminished and the incidence of cleavage on both alleles is significantly increased. ATM appears to be activated by the introduction of a double-strand break on one allele to act in trans on the uncleaved allele, repositioning or maintaining it at PCH, to prevent bi-allelic recombination and chromosomal translocations
— id: 138156, year: 2010, vol: 1, page: 23, stat: Journal Article,

Chromosome dynamics and the regulation of V(D)J recombination
Hewitt, Susannah L; Chaumeil, Julie; Skok, Jane A
2010 Sep;237(1):43-54, Immunological reviews
Perhaps no process has provided more insight into the fine manipulation of locus accessibility than antigen receptor rearrangement. V(D)J recombination is carried out by the lymphoid-specific recombination-activating (RAG 1 and 2) proteins and the non-homologous end joining machinery; yet, it occurs only at specific loci (or portions of loci) during specific developmental stages. This spatiotemporal restriction of recombination is achieved through precise alterations in locus accessibility. In this article, we discuss the work of our laboratory in elucidating how nuclear sublocalization, chromosome conformation, and locus interactions contribute to regulating this complex process. We also discuss what is known about how key factors in B-cell development (such as the ubiquitously expressed helix loop helix protein E2A, the B-cell specific transcription factors EBF1 and Pax5, and the interleukin-7 cytokine signaling pathway) exert their effects through changes in nuclear dynamics
— id: 111975, year: 2010, vol: 237, page: 43, stat: Journal Article,

Epigenetic regulation of V(D)J recombination
Johnson, Kristen; Chaumeil, Julie; Skok, Jane A
2010 Sep 20;48(1):221-243, Essays in biochemistry
Chromosome breaks are dangerous business, carrying the risk of loss of genetic information or, even worse, misrepair of the break, leading to outcomes such as dicentric chromosomes or oncogenic translocations. Yet V(D)J recombination, a process that breaks, rearranges and repairs chromosomes, is crucial to the development of the adaptive immune system, for it gives B- and T-cells the capacity to generate a virtually unlimited repertoire of antigen receptor proteins to combat an equally vast array of antigens. To minimize the risks inherent in chromosomal breakage, V(D)J recombination is carefully orchestrated at multiple levels, ranging from DNA sequence requirements all the way up to chromatin conformation and nuclear architecture. In the present chapter we introduce various regulatory controls, with an emphasis on epigenetic mechanisms and recent work that has begun to elucidate their interdependence
— id: 112204, year: 2010, vol: 48, page: 221, stat: Journal Article,

Protein targets of inflammatory serine proteases and cardiovascular disease
Sharony, Ram; Yu, Pey-Jen; Park, Joy; Galloway, Aubrey C; Mignatti, Paolo; Pintucci, Giuseppe
2010 ;7:45-45, Journal of inflammation (London, England)
ABSTRACT: Serine proteases are a key component of the inflammatory response as they are discharged from activated leukocytes and mast cells or generated through the coagulation cascade. Their enzymatic activity plays a major role in the body's defense mechanisms but it has also an impact on vascular homeostasis and tissue remodeling. Here we focus on the biological role of serine proteases in the context of cardiovascular disease and their mechanism(s) of action in determining specific vascular and tissue phenotypes. Protease-activated receptors (PARs) mediate serine protease effects; however, these proteases also exert a number of biological activities independent of PARs as they target specific protein substrates implicated in vascular remodeling and the development of cardiovascular disease thus controlling their activities. In this review both PAR-dependent and -independent mechanisms of action of serine proteases are discussed for their relevance to vascular homeostasis and structural/functional alterations of the cardiovascular system. The elucidation of these mechanisms will lead to a better understanding of the molecular forces that control vascular and tissue homeostasis and to effective preventative and therapeutic approaches
— id: 112200, year: 2010, vol: 7, page: 45, stat: Journal Article,

V(D)J recombination: a paradigm for studying chromosome interactions in mammalian cells
Skok, JA
2010 APR ;2(2):175-177, Epigenomics
— id: 110154, year: 2010, vol: 2, page: 175, stat: Journal Article,

RAG-1 and ATM coordinate monoallelic recombination and nuclear positioning of immunoglobulin loci
Hewitt, Susannah L; Yin, Bu; Ji, Yanhong; Chaumeil, Julie; Marszalek, Katarzyna; Tenthorey, Jeannette; Salvagiotto, Giorgia; Steinel, Natalie; Ramsey, Laura B; Ghysdael, Jacques; Farrar, Michael A; Sleckman, Barry P; Schatz, David G; Busslinger, Meinrad; Bassing, Craig H; Skok, Jane A
2009 Jun;10(6):655-664, Nature immunology
Coordinated recombination of homologous antigen receptor loci is thought to be important for allelic exclusion. Here we show that homologous immunoglobulin alleles pair in a stage-specific way that mirrors the recombination patterns of these loci. The frequency of homologous immunoglobulin pairing was much lower in the absence of the RAG-1-RAG-2 recombinase and was restored in Rag1-/- developing B cells with a transgene expressing a RAG-1 active-site mutant that supported DNA binding but not cleavage. The introduction of DNA breaks on one immunoglobulin allele induced ATM-dependent repositioning of the other allele to pericentromeric heterochromatin. ATM activated by the cleaved allele acts in trans on the uncleaved allele to prevent biallelic recombination and chromosome breaks or translocations
— id: 99020, year: 2009, vol: 10, page: 655, stat: Journal Article,

Association between the Igk and Igh immunoglobulin loci mediated by the 3' Igk enhancer induces 'decontraction' of the Igh locus in pre-B cells
Hewitt, Susannah L; Farmer, Deborah; Marszalek, Katarzyna; Cadera, Emily; Liang, Hong-Erh; Xu, Yang; Schlissel, Mark S; Skok, Jane A
2008 Apr;9(4):396-404, Nature immunology
Variable-(diversity)-joining (V(D)J) recombination at loci encoding the immunoglobulin heavy chain (Igh) and immunoglobulin light chain (Igk) takes place sequentially during successive stages in B cell development. Using three-dimensional DNA fluorescence in situ hybridization, here we identify a lineage-specific and stage-specific interchromosomal association between these two loci that marks the transition between Igh and Igk recombination. Colocalization occurred between pericentromerically located alleles in pre-B cells and was mediated by the 3' Igk enhancer. Deletion of this regulatory element prevented association of the Igh and Igk loci, inhibited pericentromeric recruitment and locus 'decontraction' of an Igh allele, and resulted in greater distal rearrangement of the gene encoding the variable heavy-chain region. Our data indicate involvement of the Igk locus and its 3' enhancer in directing the Igh locus to a repressive nuclear subcompartment and inducing the Igh locus to decontract
— id: 78360, year: 2008, vol: 9, page: 396, stat: Journal Article,

Regulation of immunoglobulin light-chain recombination by the transcription factor IRF-4 and the attenuation of interleukin-7 signaling
Johnson, Kristen; Hashimshony, Tamar; Sawai, Catherine M; Pongubala, Jagan M R; Skok, Jane A; Aifantis, Iannis; Singh, Harinder
2008 Mar;28(3):335-345, Immunity
Productive rearrangement of the immunoglobulin heavy-chain locus triggers a major developmental checkpoint that promotes limited clonal expansion of pre-B cells, thereby culminating in cell-cycle arrest and rearrangement of light-chain loci. By using Irf4-/-Irf8-/- pre-B cells, we demonstrated that two pathways converge to synergistically drive light-chain rearrangement, but not simply as a consequence of cell-cycle exit. One pathway was directly dependent on transcription factor IRF-4, whose expression was elevated by pre-B cell receptor signaling. IRF-4 targeted the immunoglobulin 3'Ekappa and Elambda enhancers and positioned a kappa allele away from pericentromeric heterochromatin. The other pathway was triggered by attenuation of IL-7 signaling and activated the iEkappa enhancer via binding of the transcription factor E2A. IRF-4 also regulated expression of chemokine receptor Cxcr4 and promoted migration of pre-B cells in response to the chemokine ligand CXCL12. We propose that IRF-4 coordinates the two pathways regulating light-chain recombination by positioning pre-B cells away from IL-7-expressing stromal cells
— id: 81074, year: 2008, vol: 28, page: 335, stat: Journal Article,

Silencing and nuclear repositioning of the lambda5 gene locus at the pre-B cell stage requires Aiolos and OBF-1
Karnowski, Alexander; Cao, Chun; Matthias, Gabriele; Carotta, Sebastian; Corcoran, Lynn M; Martensson, Inga-Lill; Skok, Jane A; Matthias, Patrick
2008 ;3(10):e3568-e3568, PLoS ONE
The chromatin regulator Aiolos and the transcriptional coactivator OBF-1 have been implicated in regulating aspects of B cell maturation and activation. Mice lacking either of these factors have a largely normal early B cell development. However, when both factors are eliminated simultaneously a block is uncovered at the transition between pre-B and immature B cells, indicating that these proteins exert a critical function in developing B lymphocytes. In mice deficient for Aiolos and OBF-1, the numbers of immature B cells are reduced, small pre-BII cells are increased and a significant impairment in immunoglobulin light chain DNA rearrangement is observed. We identified genes whose expression is deregulated in the pre-B cell compartment of these mice. In particular, we found that components of the pre-BCR, such as the surrogate light chain genes lambda5 and VpreB, fail to be efficiently silenced in double-mutant mice. Strikingly, developmentally regulated nuclear repositioning of the lambda5 gene is impaired in pre-B cells lacking OBF-1 and Aiolos. These studies uncover a novel role for OBF-1 and Aiolos in controlling the transcription and nuclear organization of genes involved in pre-BCR function
— id: 105353, year: 2008, vol: 3, page: e3568, stat: Journal Article,

Jane Skok: choreography of allelic exclusion.
Skok, Jane
2008 Jul 7;205(7):1514-1515, Journal of experimental medicine
— id: 81075, year: 2008, vol: 205, page: 1514, stat: Journal Article,

Dynamic changes in accessibility, nuclear positioning, recombination, and transcription at the Ig kappa locus
Fitzsimmons, Sean P; Bernstein, Ralph M; Max, Edward E; Skok, Jane A; Shapiro, Marjorie A
2007 Oct 15;179(8):5264-5273, Journal of immunology
The 3-megabase Igkappa locus undergoes differentially controlled nuclear positioning events and chromatin structural changes during the course of B cell development. The temporal association of chromatin structural changes, transcription, and recombination at the Igkappa locus was determined in a murine pre-B cell line that can be induced to recombine at the Igkappa locus and in ex vivo-cultured murine pre-B cells. Additionally, the timing of nuclear positioning relative to the temporal order of chromatin structural changes and recombination and transcription was determined. We demonstrate that before induction, the Igkappa locus was poised for recombination; both alleles were in a contracted state, and the enrichment of histone modifications and germline transcripts of specific Vkappa genes were observed. Histone modifications of the Vkappa genes did not vary upon induction but the levels of modifications correlated with the levels of germline Vkappa gene transcripts and recombination. Upon induction, but before VkappaJkappa recombination, centromeric recruitment of single Igkappa alleles occurred. DNase I sensitivity of the entire locus increased gradually over the course of differentiation while the enrichment of histone modifications downstream of the Vkappa genes was increased in the silencer regions upstream of Jkappa1, within the Igkappa sterile transcript, the kappa constant region, the Ekappai and Ekappa3' enhancers, and the recombining sequence. The ex vivo pre-B cells showed similar patterns of histone modifications across the locus except at the Vkappa genes. In this study, H3 acetylation correlated with levels of germline transcripts while H3 methylation correlated with levels of recombination
— id: 81073, year: 2007, vol: 179, page: 5264, stat: Journal Article,

Transcriptional regulation in early B cell development
Fuxa, Martin; Skok, Jane A
2007 Apr;19(2):129-136, Current opinion in immunology
Transcription factors and signalling molecules are important for both lineage commitment and lineage-specific regulation. The B cell specification factor Pax5 plays a dual role in B lineage commitment. Simultaneously, it potentiates and limits lineage choice by activating genes that are required for the B cell program while repressing lineage-inappropriate genes; more than 100 of the latter have now been identified. In this context, repression of the tyrosine kinase Flt3 has been shown to be essential for B lineage commitment. Regulation of antigen receptor recombination constitutes another level at which lineage specificity is determined, and the identification of two factors, E47 and FOXP1, which regulate the activity of the recombinase enzymes in B lineage cells, provides insight into the mechanisms that determine this. New information regarding the control of ordered recombination and allelic exclusion comes from studies of cis-acting elements within the Ig loci
— id: 70842, year: 2007, vol: 19, page: 129, stat: Journal Article,

Yin Yang 1 is a critical regulator of B-cell development
Liu, Huifei; Schmidt-Supprian, Marc; Shi, Yujiang; Hobeika, Elias; Barteneva, Natasha; Jumaa, Hassan; Pelanda, Roberta; Reth, Michael; Skok, Jane; Rajewsky, Klaus; Shi, Yang
2007 May 15;21(10):1179-1189, Genes & development
The role of the transcription factor Yin Yang 1 (YY1) in development is largely unknown. Here we show that specific ablation of YY1 in mouse B cells caused a defect in somatic rearrangement in the immunoglobulin heavy-chain (IgH) locus and a block in the progenitor-B-to-precursor-B-cell transition, which was partially rescued by a prerearranged IgH transgene. Three-dimensional DNA fluorescence in situ hybridization analysis revealed an important function for YY1 in IgH locus contraction, a process indispensable for distal V(H) to D(H)J(H) recombination. We provide evidence that YY1 binds the intronic Ei mu enhancer within the IgH locus, consistent with a direct role for YY1 in V(H)D(H)J(H) recombination. These findings identified YY1 as a critical regulator of early B-cell development
— id: 81072, year: 2007, vol: 21, page: 1179, stat: Journal Article,

Reversible contraction by looping of the Tcra and Tcrb loci in rearranging thymocytes
Skok, Jane A; Gisler, Ramiro; Novatchkova, Maria; Farmer, Deborah; de Laat, Wouter; Busslinger, Meinrad
2007 Apr;8(4):378-387, Nature immunology
Reversible contraction of immunoglobulin loci juxtaposes the variable (V) genes next to the (diversity)-joining-constant ((D)JC) gene domain, thus facilitating V-(D)J recombination. Here we show that the T cell receptor beta (Tcrb) and T cell receptor alphadelta (Tcra-Tcrd) loci also underwent long-range interactions by looping in double-negative and double-positive thymocytes, respectively. Contraction of the Tcrb and Tcra loci occurred in rearranging thymocytes and was reversed at the next developmental stage. Decontraction of the Tcrb locus probably prevented further V(beta)-DJ(beta) rearrangements in double-positive thymocytes by separating the V(beta) genes from the DJC(beta) domain. In most double-negative cells, one Tcrb allele was recruited to pericentromeric heterochromatin. Such allelic positioning may facilitate asynchronous V(beta)-DJ(beta) recombination. Hence, pericentromeric recruitment and locus 'decontraction' seem to contribute to the initiation and maintenance of allelic exclusion at the Tcrb locus
— id: 70841, year: 2007, vol: 8, page: 378, stat: Journal Article,

Epigenetic ontogeny of the Igk locus during B cell development
Goldmit, Maya; Ji, Yanhong; Skok, Jane; Roldan, Esther; Jung, Steffen; Cedar, Howard; Bergman, Yehudit
2005 Feb;6(2):198-203, Nature immunology
To become accessible for rearrangement, the immunoglobulin kappa locus must undergo a series of epigenetic changes. This begins in pro-B cells with the relocation of both immunoglobulin kappa alleles from the periphery to the center of the nucleus. In pre-B cells, one allele became preferentially packaged into an active chromatin structure characterized by histone acetylation and methylation of histone H3 lysine 4, while the other allele was recruited to heterochromatin, where it was associated with heterochromatin protein-gamma and Ikaros. These events in cis made only one allele accessible to trans-acting factors, such as RelB, which mediated DNA demethylation, to facilitate rearrangement. These results suggest that early B lymphoid epigenetic changes generate differential structures that serve as the basis for allelic exclusion
— id: 70844, year: 2005, vol: 6, page: 198, stat: Journal Article,

The pre-B-cell receptor induces silencing of VpreB and lambda5 transcription
Parker, Mathew J; Licence, Steve; Erlandsson, Lena; Galler, Gunther R; Chakalova, Lyubomira; Osborne, Cameron S; Morgan, Geoff; Fraser, Peter; Jumaa, Hassan; Winkler, Thomas H; Skok, Jane; Martensson, Inga-Lill
2005 Nov 16;24(22):3895-3905, EMBO journal
The pre-B-cell receptor (pre-BCR), composed of Ig heavy and surrogate light chain (SLC), signals pre-BII-cell proliferative expansion. We have investigated whether the pre-BCR also signals downregulation of the SLC genes (VpreB and lambda5), thereby limiting this expansion. We demonstrate that, as BM cells progress from the pre-BI to large pre-BII-cell stage, there is a shift from bi- to mono-allelic lambda5 transcription, while the second allele is silenced in small pre-BII cells. A VpreB1-promoter-driven transgene shows the same pattern, therefore suggesting that VpreB1 is similarly regulated and thereby defines the promoter as a target for transcriptional silencing. Analyses of pre-BCR-deficient mice show a temporal delay in lambda5 downregulation, thereby demonstrating that the pre-BCR is essential for monoallelic silencing at the large pre-BII-cell stage. Our data also suggest that SLP-65 is one of the signaling components important for this process. Furthermore, the VpreB1/lambda5 alleles undergo dynamic changes with respect to nuclear positioning and heterochromatin association, thereby providing a possible mechanism for their transcriptional silencing
— id: 70843, year: 2005, vol: 24, page: 3895, stat: Journal Article,

Locus 'decontraction' and centromeric recruitment contribute to allelic exclusion of the immunoglobulin heavy-chain gene
Roldan, Esther; Fuxa, Martin; Chong, Winnie; Martinez, Dolores; Novatchkova, Maria; Busslinger, Meinrad; Skok, Jane A
2005 Jan;6(1):31-41, Nature immunology
Allelic exclusion of immunoglobulin genes ensures the expression of a single antibody molecule in B cells through mostly unknown mechanisms. Large-scale contraction of the immunoglobulin heavy-chain (Igh) locus facilitates rearrangements between Igh variable (V(H)) and diversity gene segments in pro-B cells. Here we show that these long-range interactions are mediated by 'looping' of individual Igh subdomains. The Igk locus also underwent contraction by looping in small pre-B and immature B cells, demonstrating that immunoglobulin loci are in a contracted state in rearranging cells. Successful Igh recombination induced the rapid reversal of locus contraction in response to pre-B cell receptor signaling, which physically separated the distal V(H) genes from the proximal Igh domain, thus preventing further rearrangements. In the absence of locus contraction, only the four most proximal V(H) genes escaped allelic exclusion in immature mu-transgenic B lymphocytes. Pre-B cell receptor signaling also led to rapid repositioning of one Igh allele to repressive centromeric domains in response to downregulation of interleukin 7 signaling. These data link both locus 'decontraction' and centromeric recruitment to the establishment of allelic exclusion at the Igh locus
— id: 70845, year: 2005, vol: 6, page: 31, stat: Journal Article,

Pax5 induces V-to-DJ rearrangements and locus contraction of the immunoglobulin heavy-chain gene
Fuxa, Martin; Skok, Jane; Souabni, Abdallah; Salvagiotto, Giorgia; Roldan, Esther; Busslinger, Meinrad
2004 Feb 15;18(4):411-422, Genes & development
The subnuclear location and chromatin state of the immunoglobulin heavy-chain (IgH) locus have been implicated in the control of VDJ recombination. VH-to-DJH rearrangement of distal, but not proximal V(H) genes, furthermore, depends on the B-lineage commitment factor Pax5 (BSAP). He e we demonstrate that ectopic Pax5 expression from the Ikaros promote induces proximal rather than distal VH-DJH rearrangements in Ik(Pax5/+) thymocytes, thus recapitulating the loss-of-function phenotype of Pax5-/- pro-B cells. The phenotypic similarities of both cell types include (1) chromatin accessibility of distal VH genes in the absence of VH-DJH rearrangements, (2) expression of the B-cell-specific regulator EBF, (3) central location of IgH alleles within the nucleus, and (4) physical separation of distal VH genes from proximal segments in an extended IgH locus. Reconstitution of Pax5 expression in Pax5-/- pro-B cells induced large-scale contraction and distal VH-DJH rearrangements of the IgH locus. Hence, VH-DJH recombination is regulated in two steps during early B-lymphopoiesis. The IgH locus is first repositioned from its default location at the nuclear periphery toward the center of the nucleus, which facilitates proximal VH-DJH recombination. Pax5 subsequently activates locus contraction and distal VH-DJH rearrangements in collaboration with an unknown factor that is present in pro-B cells, but absent in thymocytes
— id: 70846, year: 2004, vol: 18, page: 411, stat: Journal Article,

C-terminal SRC kinase controls acute inflammation and granulocyte adhesion
Thomas, Richard M; Schmedt, Christian; Novelli, Marco; Choi, B Ken; Skok, Jane; Tarakhovsky, Alexander; Roes, Jurgen
2004 Feb;20(2):181-191, Immunity
To establish whether the widely expressed regulator of Src family kinases Csk contributes to the control of acute inflammation in vivo, we inactivated csk in granulocytes by conditional mutagenesis (Cre/loxP). Mutant mice (Csk-GEcre) developed acute multifocal inflammation in skin and lung. Animals were protected from the disease in a microbiologically controlled environment, but remained hypersensitive to LPS-induced shock. Csk-deficient granulocytes showed enhanced spontaneous and ligand-induced degranulation with hyperinduction of integrins. This hyperresponsiveness was associated with hyperadhesion and impaired migratory responses in vitro. Hyperphosphorylation of key signaling proteins such as Syk and Paxillin in mutant granulocytes further supported breakdown of the activation threshold set by Csk. By enforcing the need for ligand engagement Csk thus prevents premature granulocyte recruitment while supporting the motility of stimulated cells through negative regulation of cell adhesion
— id: 70847, year: 2004, vol: 20, page: 181, stat: Journal Article,

Subnuclear compartmentalization of immunoglobulin loci during lymphocyte development
Kosak, Steven T; Skok, Jane A; Medina, Kay L; Riblet, Roy; Le Beau, Michelle M; Fisher, Amanda G; Singh, Harinder
2002 Apr 5;296(5565):158-162, Science
Immunoglobulin (Ig) loci are selectively activated for transcription and rearrangement during B lymphocyte development. Using fluorescence in situ hybridization, we show that Ig heavy (H) and Igkappa loci are preferentially positioned at the nuclear periphery in hematopoietic progenitors and pro-T cells but are centrally configured in pro-B nuclei. The inactive loci at the periphery do not associate with centromeric heterochromatin. Upon localization away from the nuclear periphery in pro-B cells, the IgH locus appears to undergo large-scale compaction. We suggest that subnuclear positioning represents a novel means of regulating transcription and recombination of IgH and Igkappa loci during lymphocyte development
— id: 70848, year: 2002, vol: 296, page: 158, stat: Journal Article,

Rewiring of CD40 is necessary for delivery of rescue signals to B cells in germinal centres and subsequent entry into the memory pool
Siepmann, K; Skok, J; van Essen, D; Harnett, M; Gray, D
2001 Mar;102(3):263-272, Immunology
Memory B-cell development is impaired by in vivo blockade of the CD40-CD40 ligand (CD40L) interaction using human Fc immunoglobulin G1 (IgG1)-mouse CD40 fusion protein (CD40-Ig); however, germinal centre (GC) formation is not. We show here that the block in B-cell differentiation in these mice is at the stage of rescue from apoptosis and exit from the GC. Thus, GC from CD40-Ig-treated mice contain a three- to fourfold higher level of apoptotic cells than found in control mice injected with human IgG1 alone. This increase in apoptosis is not caused by a blockade of the CD40L-mediated rescue signal but is the result of an intrinsic defect of GC B cells in CD40-Ig-treated mice to receive rescue signals via CD40. While anti-CD40 stimulation maintained the viability in culture of GC B cells from control mice, it did not rescue GC B cells from CD40-Ig-treated mice. This data is consistent with the notion that a 'rewiring' of the CD40 molecule is induced by CD40 ligation early in the response and is necessary to allow B-cell rescue from apoptosis when they subsequently enter the GC
— id: 81071, year: 2001, vol: 102, page: 263, stat: Journal Article,

Nonequivalent nuclear location of immunoglobulin alleles in B lymphocytes
Skok, J A; Brown, K E; Azuara, V; Caparros, M L; Baxter, J; Takacs, K; Dillon, N; Gray, D; Perry, R P; Merkenschlager, M; Fisher, A G
2001 Sep;2(9):848-854, Nature immunology
Individual B lymphocytes normally express immunoglobulin (Ig) proteins derived from single Ig heavy chain (H) and light chain (L) alleles. Allelic exclusion ensures monoallelic expression of Ig genes by each B cell to maintain single receptor specificity. Here we provide evidence that at later stages of B cell development, additional mechanisms may contribute to prioritizing expression of single IgH and IgL alleles. Fluorescent in situ hybridization analysis of primary splenic B cells isolated from normal and genetically manipulated mice showed that endogenous IgH, kappa and lambda alleles localized to different subnuclear environments after activation and had differential expression patterns. However, this differential recruitment and expression of Ig alleles was not typically seen among transformed B cell lines. These data raise the possibility that epigenetic factors help maintain the monoallelic expression of Ig
— id: 70849, year: 2001, vol: 2, page: 848, stat: Journal Article,

Dendritic cell-derived IL-12 promotes B cell induction of Th2 differentiation: a feedback regulation of Th1 development
Skok, J; Poudrier, J; Gray, D
1999 Oct 15;163(8):4284-4291, Journal of immunology
B cells convert what are normally conditions for Th1 differentiation into an environment suitable for Th2 development. This capacity is dependent on CD40 as B cells from CD40-/- mice do not elicit Th2 differentiation. To elucidate the basis of this effect, we surveyed cytokine RNA made by naive B cells after activation with anti-Ig and anti-CD40. Resting B cells make TGF-beta message only, however, 4 days after activation, RNA encoding IL-6, IL-10, and TNF-alpha was found. The expression of these messages was accelerated by 2 days in the presence of IL-12. The relevance of these observations to T cell differentiation was investigated: addition of OVA peptide to splenic cells from DO.11.10 transgenic mice causes most T cells to make IFN-gamma. Coactivation of B cells in these cultures reduces the number of IFN-gamma-producing T cells and increases the number synthesizing IL-4. Abs to IL-6 and IL-10 block the IL-4 enhancement. Dissection of the component APC demonstrated that interaction of B cells with IL-12-producing dendritic cells is crucial for B cell-mediated IL-4 enhancement: Thus, B cells preactivated in the presence of dendritic cells from IL-12-/- mice show little IL-4-inducing activity when used to activate T cells. This immune regulation is initiated by IL-12 and therefore represents a feedback loop to temper its own dominant effect (IFN-gamma induction)
— id: 81070, year: 1999, vol: 163, page: 4284, stat: Journal Article,

Distinct genes for fibroblast and serum C1q
Skok, J; Solomon, E; Reid, K B; Thompson, R A
1981 Aug 6;292(5823):549-551, Nature
— id: 81069, year: 1981, vol: 292, page: 549, stat: Journal Article,