1995 Fiscal Year Final Research Report Summary
Regulation of the human epsilon-globin gene transcription in the switching mechanism
| Project/Area Number |
05680598
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Molecular biology
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| Research Institution | Nippon Medical School |
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Principal Investigator |
WADA Yuko Nippon Medical School, Dept.of Physiology I,Assistant professor, 医学部, 講師 (60234390)
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| Project Period (FY) |
1993 – 1995
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| Keywords | epsilon-globin gene / transcription / silencer / DNA bending / human globin gene |
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| Research Abstract |
The human epsilon-globin gene contains not only silencer but also several important cis-acting factors in the upstream flanking region, which regulate stage-specific switching of globin genes. Previously we characterized the human epsilon-globin gene silencer by in vitro transcription assay. Here we first examined the S1 nuclease hypersensitive sites (S1 HS) in the upstream flanking region and found that two regions were S1 HS.The unusual feature in the region, triplex DNA or slipped DNA,was most likely to be the structure that causes S1 nuclease sensitivity. We also examined bent DNA which is one of the unusual structures intrinsically adopted by the sequence. The circular permutation experiment revealed that the DNA bend sites appeared every 680 bp on average in the entire region. In order to know the periodicity of the bend sites in other globin genes, we next mapped the sites in the beta-globin gene region. The relative positions of the sites to the cap site were identical to those in the epsilon-globin gene region, suggesting that the bend sites have been conserved during molecular evolution of the genomic sequence among two genes. The result also strengthens their significance in the genomic organization such as a signal for nucleosome phasing. Finally, we mapped the bend sites in the region spanning 13.3kb containing the Ggamma-Agamma-psibeta-globin genes. The bend sites were present at an interval of roughly 700bp and they divide the region into units. Furthermore, they were conserved in the promoter region of nearly all beta-family globin genes, although the periodicity of the sites was locally disturbed at the junctions of the duplicated Ggamma-and Agamma-globin genes and their second introns. This suggested that the periodicity of the bend sites is ranked lower in the hierarchy of genomic DNA organization than genome rearrangement and gene expression.
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