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Query: UMLS:C1852044 (HS3)
 171 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stage-specific expression of the human beta-like globin genes is controlled by interactions between regulatory elements near the individual genes and additional elements located upstream in the Locus Control Region (LCR). Elucidation of the mechanisms that govern these interactions could suggest strategies to reactivate fetal (gamma) or embryonic (epsilon) genes in individuals with severe hemoglobinopathies. This study extends an earlier analysis of a transgenic construct, HS3epsilon gamma, testing: (A) the effect of substitution of HS2 for HS3 on stage-specific expression of the epsilon and gamma genes and, (B) the role of an evolutionarily conserved YY1 binding site in transcriptional regulation of the gamma gene. The data show that both HS3epsilon gamma and HS2epsilon gamma can individually support embryonic expression of epsilon and fetal expression of Agamma. Thus, the cis regulators of distinct expression patterns for epsilon and gamma are likely to reside near the genes, rather than in specific hypersensitive sites of the LCR. Alterations in Agamma expression patterns observed in transgenic lines carrying a construct with a mutation in a conserved YY1 binding site at -1086 indicate that this site might function to facilitate active transcription of the gamma gene in fetal life.
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PMID:Analysis of linked human epsilon and gamma transgenes: effect of locus control region hypersensitive sites 2 and 3 or a distal YY1 mutation on stage-specific expression patterns. 1023 7

In the work reported here we have undertaken a functional dissection of a Polycomb response element (PRE) from the iab-7 cis-regulatory domain of the Drosophila melanogaster bithorax complex (BX-C). Previous studies mapped the iab-7 PRE to an 860-bp fragment located just distal to the Fab-7 boundary. Located within this fragment is an approximately 230-bp chromatin-specific nuclease-hypersensitive region called HS3. We have shown that HS3 is capable of functioning as a Polycomb-dependent silencer in vivo, inducing pairing-dependent silencing of a mini-white reporter. The HS3 sequence contains consensus binding sites for the GAGA factor, a protein implicated in the formation of nucleosome-free regions of chromatin, and Pleiohomeotic (Pho), a Polycomb group protein that is related to the mammalian transcription factor YY1. We show that GAGA and Pho interact with these sequences in vitro and that the consensus binding sites for the two proteins are critical for the silencing activity of the iab-7 PRE in vivo.
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PMID:The iab-7 polycomb response element maps to a nucleosome-free region of chromatin and requires both GAGA and pleiohomeotic for silencing activity. 1115 16

The expression of c-myc is deregulated in Burkitt's lymphoma by the translocation t(8;14). Most of the increased c-myc expression is from the P1 promoter, which is normally a minor promoter. How the P1 promoter is activated by the immunoglobulin heavy chain gene enhancers is not understood. We identified a YY1 site in the immunoglobulin heavy-chain gene HS3 enhancer, which increased c-myc P1 promoter activity, and a MARE site, which decreased c-myc P1 activity. Small Maf proteins bound to the MARE site both in vitro and in vivo, recruited histone deacetylase 2, and resulted in deacetylation of histones H3 and H4 at the c-myc promoter region. In contrast, YY1 recruited CBP and increased histone acetylation at the c-myc promoter. Rb interacts with YY1 to prevent DNA binding in normal B cells, but no significant interaction with YY1 was detected in Burkitt's cells, and binding of YY1 to the HS3 enhancer was observed by chromatin immunoprecipitaton. Increased expression of MafK and/or decreased expression of YY1 by silencing RNA downregulated endogenous c-myc mRNA levels and increased the sensitivity of the cells to doxorubicin. Mutation of the major active sites (nuclear factor-kappa B and YY1) in the enhancers prevented c-myc activation.
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PMID:Activation of the c-myc p1 promoter in Burkitt's lymphoma by the hs3 immunoglobulin heavy-chain gene enhancer. 1728 52