Nucleic Acids Research, 1992, Vol. 20, No. 21 5527-5531
© 1992
ENZYMOLOGY |
DNA damage response of cloned DNA ß-polymerase promoter is blocked in mutant cell lines deficient in protein kinase A
Laboratory of Biochemistry, National Cancer Institute, National Institutes of Health Bethesda, MD 20892, USA
* To whom correspondence should be addressed at: Sealy Center for Molecular Science, H-51, University of Texas Medical Branch, Galveston, TX 77555-0851, USA
Received September 21, 1992. Accepted September 25, 1992.
DNA ß3-polymerase (ß-pol), one of the recognized DNA polymerizing enzymes in vertebrates, has a role in ‘very short patch’ gap-filling synthesis during nucleotide excision DNA repair. In human and mouse, the enzyme is encoded by a single-copy gene located on the short arm of chromosome 8 near the centromere. In a series of studies, we have found that the cloned human ß-pol promoter is regulated by signals acting through the single ATF/CRE palindrome in the core promoter. These signals include transactivation by: adenovirus E1a/E1b proteins; activated p21ras; and in CHO cells, treatment with the DNA damaging agent MNNG. Hence, several types of stimulatory signals are mediated through the single ATF/CRE site, including DNA damage induction. To understand the mechanism of ß-pol promoter activation by MNNG in CHO cells, we asked whether induction of the cAMP/protein kinase A pathway can increase transcription of the cloned promoter in this system. Agents that increase cellular cAMP levels (8-BrcAMP; forskolin and IBMx) activated the ß-pol promoter fusion gene in transient expression experiments, and a mutation in the ATF/CRE palindrome blocked this response. Thus, the ATF/CRE site appears to be cAMP responsive in the CHO cell system. We found that the activation of the cloned ß-pol promoter by MNNG does not occur with two mutant CHO cell lines that are deficient in protein kinase A activity. Further, simultaneous treatment of wild-type CHO cells, with MNNG and to elevate cAMP, failed to result in an additive effect for activation of the /-pol promoter. Thus, these effectors may act through a common pathway. These results suggest that the activation of the cloned ß-pol promoter in CHO cells following MNNG treatment is mediated through the cAMP/protein kinase A signal transduction pathway.
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