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Preferential modification of GC boxes by benzo[a]pyrene-7,8-diol-9,10-epoxide
A Kootstra1, L K Lew, R S Nairn
1Department of Carcinogenesis, University of Texas M. D. Anderson Cancer Center, Smithville.
Molecular Carcinogenesis
|January 1, 1989
Summary
The ultimate carcinogen anti-benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE-I) preferentially binds to GC-box sequences in the Chinese hamster ovary aprt gene
Area of Science:
- Molecular biology
- Carcinogenesis research
- Genetics
Background:
- Benzo[a]pyrene is an ultimate carcinogen.
- BPDE-I is the ultimate carcinogen derived from benzo[a]pyrene.
- The Chinese hamster ovary aprt gene is a target for DNA damage.
Purpose of the Study:
- To determine the distribution of BPDE-I binding sites in the 5' region of the Chinese hamster ovary aprt gene.
- To investigate the relationship between BPDE-I binding and transcriptional activity.
Main Methods:
- Construction of a plasmid (pGAL) containing the hamster aprt gene and flanking regions.
- In vitro transcription using T7 RNA polymerase on BPDE-I-modified pGAL.
- Laser cutting technique to map BPDE-I DNA binding sites.
Main Results:
- Two prominent transcriptional stop sites were identified in vitro.
- One stop site was in the first exon, the second was upstream of the translational start site.
- The upstream region containing GC-box consensus sequences was a hot spot for BPDE-I modification.
Conclusions:
- BPDE-I modification occurs preferentially at GC-box sequences in the 5' flanking region of the aprt gene.
- These GC-box regions are potential Sp1 binding sites.
- BPDE-I binding may influence gene transcription.