Aug 8, 1998

Effects of nonbulky DNA base damages on Escherichia coli RNA polymerase-mediated elongation and promoter clearance

The Journal of Biological Chemistry
A Viswanathan, Paul W Doetsch


DNA base damage products either formed spontaneously or as a result of exposure to various genotoxic agents were examined for their effects on Escherichia coli RNA polymerase-mediated transcription in vitro. Uracil, O6-methylguanine (O6-meG), and 8-oxoguanine (8-oxoG) were placed at specific sites downstream from the transcriptional start site on the transcribed strand of a duplex template under the control of the strong tac promoter. In vitro, single-round transcription experiments carried out with purified E. coli RNA polymerase revealed efficient bypass at the three lesions examined and subsequent generation of full-length runoff transcripts. Transcript sequence analysis revealed that E. coli RNA polymerase inserted primarily adenine into the transcript opposite to uracil, uracil opposite to O6-meG, and either adenine or cytosine opposite to 8-oxoG. Thus, a uracil in the DNA template resulted in a G-to-A transition mutation in the lesion bypass product whereas O6-meG produced a C-to-U transition mutation and 8-oxoG generated either the correct transcriptional product or a C-to-A transversion mutation. When 8-oxoG was placed within close proximity to the transcriptional start site (within the region required for effective pro...Continue Reading

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Mentioned in this Paper

Alkalescens-Dispar Group
DNA Repair
DNA-Directed RNA Polymerase
RNA Polymerase Assembly Pathway
Transcription, Genetic
Gene Expression
Sequence Analysis

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