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Molecular Cloning and Characterization of the Promoter for the Chinese Hamster DNA Topoisomerase II Gene
To investigate the mechanisms governing the expression of DNA topoisomerase IIα, the Chinese hamster topoisomerase IIα gene has been cloned and the promoter region analyzed. There are several transcriptional start sites clustered in a region of 30 base pairs, with the major one being 102 nucleotid...
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Published in: | The Journal of biological chemistry 1995-10, Vol.270 (43), p.25850 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Online Access: | Get full text |
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Summary: | To investigate the mechanisms governing the expression of DNA topoisomerase IIα, the Chinese hamster topoisomerase IIα gene
has been cloned and the promoter region analyzed. There are several transcriptional start sites clustered in a region of 30
base pairs, with the major one being 102 nucleotides upstream from the ATG translation initiation site. Sequencing data reveal
one GC box and a total of five inverted CCAAT elements (ICEs) within a region of 530 base pairs upstream from the major transcription
start site. Sequence comparison between the human and Chinese hamster topoisomerase IIα gene promoter regions shows a high
degree of homology centered at the ICEs and GC box. In vitro DNase I footprinting results indicate protection by binding proteins at and around each ICE on both DNA strands. However,
no obvious protection was observed for the GC box. Competition gel mobility shift assays with oligonucleotides containing
either the wild-type or mutated ICE sequences suggest that identical or similar proteins specifically bind at each ICE, although
with different affinities for individual ICE sequences. Chloramphenicol acetyltransferase assays employing nested 5â²-deletions
of the 5â²-flanking sequence of the gene demonstrate that the sequence between â186 and +102, which contains three proximal
ICEs, is sufficient for near wild-type level of promoter activity. When these three ICEs were gradually replaced with sequences
which do not interact with the binding proteins, reducing promoter activity of the resulted constructs was observed. In conjunction
with results from footprinting and gel mobility shift studies, the transient gene expression finding suggests that the ICEs
are functionally important for the transcriptional regulation of the topoisomerase IIα gene. |
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ISSN: | 0021-9258 1083-351X |
DOI: | 10.1074/jbc.270.43.25850 |