Activation of immunoglobulin mu gene expression involves stepwise demethylation.

Gerondakis, Steven Demetrious; Boyd, Aoife; Bernard, Ora; Webb, Elizabeth; Adams, Jerry M.

doi:10.1002/j.1460-2075.1984.tb02248.x

Cited by 21 publications

(10 citation statements)

References 57 publications

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“…The domain of histone acetylation in the globin locus spans both transcriptionally active and inactive genes and encompasses both demethylated and methylated DNA. In our experiments, we also note that demethylation is neither necessary for nor a consequence of transcription, consistent with previous finding of partial demethylation of the endogenous µ locus in pre-B cells (Gerondakis et al 1984). Thus, the extended histone acetylation in the premethylated µ gene may not be linked to DNA demethylation.…”

Section: Mars Mediate Long-range µ Enhancer Function and Histone Acetsupporting

confidence: 92%

Nuclear matrix attachment regions antagonize methylation-dependent repression of long-range enhancer-promoter interactions

Forrester

Fernández²,

Grosschedl³

1999

Genes & Development

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The immunoglobulin intragenic µ enhancer region acts as a locus control region that mediates transcriptional activation over large distances in germ line transformation assays. In transgenic mice, but not in transfected tissue culture cells, the activation of a variable region (V H ) promoter by the µ enhancer is dependent on flanking nuclear matrix attachment regions (MARs). Here, we examine the effects of DNA methylation, which occurs in early mouse development, on the function of the µ enhancer and the MARs. We find that methylation of rearranged µ genes in vitro, before transfection, represses the ability of the µ enhancer to activate the V H promoter over the distance of 1.2 kb. However, methylation does not affect enhancer-mediated promoter activation over a distance of 150 bp. In methylated DNA templates, the µ enhancer alone induces only local chromatin remodeling, whereas in combination with MARs, the µ enhancer generates an extended domain of histone acetylation. These observations provide evidence that DNA methylation impairs the distance independence of enhancer function and thereby imposes a requirement for additional regulatory elements, such as MARs, which facilitate long-range chromatin remodeling. Transcriptional activation of genes in mice has been shown to depend on enhancers or locus control regions (LCRs) (for review, see Dillon and Grosveld 1994;Martin et al. 1996). LCRs, described initially for the human ␤-globin locus, are required for the formation of an "open," DNase I-sensitive chromatin domain before transcriptional activation (Forrester et al. 1987;Jimenez et al. 1992). In transgenic mice, LCRs are functionally defined as elements that mediate developmentally regulated expression of linked transgenes at physiological levels, independent of the site of chromosomal integration (Grosveld et al. 1987). In addition, these sequences overcome variegation of gene expression at the single cell level (Festenstein et al. 1996;Walters et al. 1996). LCRs have been identified in many genes and are composite sequence elements that typically contain an enhancer combined with auxiliary sequences. Although the role of enhancers in chromatin accessibility and transcriptional activation of linked promoters has been studied extensively (for review, see Blackwood and Kadonaga 1998), the functions of the auxiliary sequences remain obscure.The immunoglobulin µ heavy chain locus contains an intragenic enhancer region that can function as an LCR to activate a distal variable region (V H ) promoter or a heterologous promoter in germ-line transformation assays (Adams et al. 1985;Jenuwein and Grosschedl 1991). The 1-kb µ enhancer region includes a well-characterized transcriptional enhancer (for review, see Ernst and Smale 1995), the promoter for germ-line noncoding Iµ transcripts (Lennon and Perry 1985), and nuclear matrix attachment regions (MARs) that flank the enhancer on either side (Cockerill et al. 1987). In transgenic mice, the MARs augment the function of the µ enhancer in activating the V H promoter by...

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Section: Mars Mediate Long-range µ Enhancer Function and Histone Acetsupporting

confidence: 92%

Nuclear matrix attachment regions antagonize methylation-dependent repression of long-range enhancer-promoter interactions

Forrester

Fernández²,

Grosschedl³

1999

Genes & Development

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“…which JH loci are still in the germline context (26 locus in one of the aforementioned unusual A-MuLV transformants was also found to occur without hypomethylation (28). These observations indicate that transcriptional competence of immunoglobulin genes can be established without significant undermethylation.…”

Section: Discussionmentioning

confidence: 67%

Inducible transcription of the unrearranged kappa constant region locus is a common feature of pre-B cells and does not require DNA or protein synthesis.

Nelson¹,

Kelley²,

Perry³

1985

Proc. Natl. Acad. Sci. U.S.A.

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Transcription of unrearranged K constant region (KO) loci is dramatically induced in pre-B cells transformed by the Abelson murine leukemia virus when the cells are exposed to bacterial lipopolysaccharide (LPS). Transcriptional activity, detected both by accumulation of the 8-kilobase ic" RNA product and by nuclear run-on measurements, is evident within a few hours after exposure to LPS and continues to increase over a 24-hr period. CK (5,6). Like its viral counterparts, the C,. enhancer can increase transcription from distal promoters in either orientation and appears to influence local chromatin structure (7,8). A notable feature of the enhancer is its role in helping to define tissue-specific expression of K genes. When productively rearranged K genes are transfected into cell lines or are introduced into transgenic mice, they are efficiently and accurately expressed only in cells of lymphoid origin (5, 9). Other genes linked to the K enhancer also exhibit such tissue specificity (6). These observations suggest that the ability of the K enhancer to regulate transcriptional activity may require interaction with a trans-acting soluble factor(s) found only in lymphoid cells. Indeed, recent studies of the immunoglobulin heavy-chain enhancer have identified protein binding sites in a region containing a sequence motif that is shared by the K enhancer (10). Although promoter elements are also clearly important in determining the transcriptional activity of K genes, the enhancer seems to have a dominant role in the regulatory hierarchy, at least in mature plasma cells (11).In earlier studies of a B-cell-lymphoma line, 70Z/3, which has the unusual property of being inducible for K light-chain synthesis by the mitogen bacterial lipopolysaccharide (LPS), it was shown that LPS treatment elicits a dramatic increase in transcriptional activity and a concomitant alteration in the chromatin structure encompassing the K enhancer element (7,12). Both the productively rearranged K gene and the germline K allele exhibited transcriptional activation and altered chromatin structure, leading us to speculate that the inductive effect is directed at the K enhancer rather than the V1K promoter.In this report, we demonstrate that LPS-inducible transcriptional competence of the K locus is not a peculiarity of the 70Z/3 line, but rather is a characteristic of a discrete stage of B-cell ontogeny near the pre-B-cell to B-cell transition. Moreover, we show that the induction of transcription can occur in the absence of DNA or protein synthesis. These results suggest a model for B-cell development in which an external signal may initiate expression of the K locus by modifying or overriding the activity of an enhancer-specific factor. MATERIALS AND METHODSThe Abelson murine leukemia virus (A-MuLV)-transformed cell lines were obtained from David Baltimore and propagated in RPMI 1640 medium (GIBCO) supplemented with 10% heat-inactivated fetal calf serum. LPS (Difco; Escherichia coli 0111:B4) was used at a final concentration of 10 Ag/...

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“…Alternatively, the relevant change in IgH gene structure might precede the change in K gene structure, in which case enhancer independence of IgH expression would occur at an earlier stage. From the available data on the methylation status of IgH genes in cell lines representing different developmental stages (5,9,30), it would appear that IgH hypomethylation is gradual, occurring first at the 5' end of the gene in pre-B cells and later at the 3' end of the gene in B cells. Which, if any, of these changes is related to the shift towards enhancer independence remains to be established.…”

Section: Resultsmentioning

confidence: 99%

The coupling between enhancer activity and hypomethylation of kappa immunoglobulin genes is developmentally regulated.

Kelley¹,

Pollok²,

Atchison³

et al. 1988

Mol. Cell. Biol.

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Previous studies have indicated that immunoglobulin enhancers are essential for establishing transcriptional competence but not for maintaining the activity of constitutively transcribed genes. To understand the basis for this developmental shift away from dependence on enhancer function, we have investigated the relationship between transcriptional activity and methylation status of the immunoglobulin K light-chain genes (K genes) in mouse cell lines representing different stages of B-cel maturation. Using pre-B-cell lines in which the level of a critical K enhancer-binding factor, NF-KB, was controlled by the administration or withdrawal of lipopolysaccharide and plasmacytoma lines that either contain or lack this factor, we studied the properties of endogenous K genes and of transfected K genes which were stably integrated into the genomes of these cells. In the pre-B ceUls, the exogenous (originally unmethylated) K genes, as well as the endogenous K genes, were fully methylated and persistently dependent on enhancer function, even after more than 30 generations in a transcriptionally active state. In plasmacytoma cels, the endogenous K genes were invariably hypomethylated, whereas exogenous K genes were hypomethylated only in cells that contain NF-KB and are thus permissive for K enhancer function. These results indicate that the linkage of hypomethylation to enhancer-dependent activation of K transcription occurs after the pre-B-cell stage of development. The change in methylation status, together with associated changes in chromatin structure, may suffice to eliminate or lessen the importance of the enhancer for the maintenance of the transcriptionally active state.

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Activation of immunoglobulin mu gene expression involves stepwise demethylation.

Cited by 21 publications

References 57 publications

Nuclear matrix attachment regions antagonize methylation-dependent repression of long-range enhancer-promoter interactions

Nuclear matrix attachment regions antagonize methylation-dependent repression of long-range enhancer-promoter interactions

Inducible transcription of the unrearranged kappa constant region locus is a common feature of pre-B cells and does not require DNA or protein synthesis.

The coupling between enhancer activity and hypomethylation of kappa immunoglobulin genes is developmentally regulated.

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