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The Ig? gene enhancers, E3' and Ed, are essential for triggering transcription.

ABSTRACT: The mouse Ig? gene locus has three known transcriptional enhancers: an intronic enhancer (Ei), a 3' enhancer (E3'), and a further downstream enhancer (Ed). Previous studies on B lymphocytes derived from mutant embryonic stem cells have shown that deletion of either Ei or E3' significantly reduces Ig? gene rearrangement, whereas the combined deletion of both Ei and E3' eliminates such recombination. Furthermore, deletion of either E3' or Ed significantly reduces rearranged Ig? gene transcription. To determine whether the combined presence of both E3' and Ed are essential for Ig? gene expression, we generated homozygous double knockout (DKO) mice with targeted deletions in both elements. Significantly, homozygous DKO mice were unable to generate ?(+) B cells both in bone marrow and the periphery and exhibited surface expression almost exclusively of Ig?-chains, despite the fact that they possessed potentially functional rearranged Ig? genes. Compared with their single-enhancer-deleted counterparts, Ig? loci in homozygous DKO mice exhibited dramatically reduced germline and rearranged gene transcription, lower levels of gene rearrangement and histone H3 acetylation, and markedly increased DNA methylation. This contributed to a partial developmental block at the pre-B cell stage of development. We conclude that the two downstream enhancers are essential in Ig? gene expression and that Ei in homozygous DKO mice is incapable of triggering Ig? gene transcription. Furthermore, these results reveal unexpected compensatory roles for Ed in E3' knockout mice in triggering germline transcription and V? gene rearrangements to both J? and RS elements.

SUBMITTER: Zhou X

PROVIDER: S-EPMC3059262 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature

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The Igκ gene enhancers, E3' and Ed, are essential for triggering transcription.

Zhou Xiaorong X Xiang Yougui Y Garrard William T WT

Journal of immunology (Baltimore, Md. : 1950) 20101112 12

The mouse Igκ gene locus has three known transcriptional enhancers: an intronic enhancer (Ei), a 3' enhancer (E3'), and a further downstream enhancer (Ed). Previous studies on B lymphocytes derived from mutant embryonic stem cells have shown that deletion of either Ei or E3' significantly reduces Igκ gene rearrangement, whereas the combined deletion of both Ei and E3' eliminates such recombination. Furthermore, deletion of either E3' or Ed significantly reduces rearranged Igκ gene transcription. ...[more]

PMID: 21076060

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Project description:The vitamin D receptor (VDR) mediates the endocrine actions of 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] and autoregulates the expression of its own gene in target cells. In studies herein, we used chromatin immunoprecipitation-chip analyses to examine further the activities of 1,25(OH)(2)D(3) and to assess the consequences of VDR/retinoid X receptor heterodimer binding at the VDR gene locus. We also explored mechanisms underlying the ability of retinoic acid, dexamethasone, and the protein kinase A activator forskolin to induce VDR up-regulation as well. We confirmed two previously identified intronic 1,25(OH)(2)D(3)-inducible enhancers and discovered two additional regions, one located 6 kb upstream of the VDR transcription start site. Although RNA polymerase II was present at the transcription start site in the absence of 1,25(OH)(2)D(3), it was strikingly up-regulated at both this site and at individual enhancers in its presence. 1,25(OH)(2)D(3) also increased basal levels of H4 acetylation at these enhancers as well. Surprisingly, many of these enhancers were targets for CCAAT enhancer-binding protein-beta and runt-related transcription factor 2; a subset also bound cAMP response element binding protein, retinoic acid receptor, and glucocorticoid receptor. Unexpectedly, many of these factors were resident at the Vdr gene locus in the absence of inducer, suggesting that they might contribute to basal Vdr gene expression. Indeed, small interfering RNA down-regulation of CCAAT enhancer-binding protein-beta suppressed basal VDR expression. These regulatory activities of 1,25(OH)(2)D(3), forskolin, and dexamethasone were recapitulated in MC3T3-E1 cells stably transfected with a full-length VDR bacterial artificial chromosome (BAC) clone-luciferase reporter gene. Finally, 1,25(OH)(2)D(3) also induced accumulation of VDR and up-regulated H4 acetylation at conserved regions in the human VDR gene. These data provide important new insights into VDR gene regulation in bone cells.

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The Ig? gene enhancers, E3' and Ed, are essential for triggering transcription.

Publications

The Igκ gene enhancers, E3' and Ed, are essential for triggering transcription.

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