EFFECTS OF AMINOFLUORENE AND ACETYLAMINOFLUORENE DNA-ADDUCTS ON TRANSCRIPTIONAL ELONGATION BY RNA-POLYMERASE-II

A prominent model for the mechanism of transcription-coupled DNA repai r proposes that an arrested RNA polymerase directs the nucleotide exci sion repair complex to the transcription-blocking lesion,The specific role for RNA polymerase II in this mechanism can be examined by compar ing the extent of polymerase arrest with the extent of transcription-c oupled repair for a specific DNA lesion, Previously we reported that a cyclobutane pyrimidine dimer that is repaired preferentially in trans cribed genes is a strong block to transcript elongation by RNA pol II (Donahue, B. A., Yin, S.,Taylor, J.-S., Reines, D., and Hanawalt, P. C . (1994) Proc. Natl. Acad. Sci. U.S.A. 91, 8502-8506), Here we report the extent of RNA polymerase II arrest by the C-8 guanine DNA adduct f ormed by N-2-aminofluorene, a lesion that does not appear to be prefer entially repaired, Templates for an in vitro transcription assay were constructed with either an N-2-aminofluorene adduct or the helix-disto rting N-2-acetylaminofluorene adduct situated at a specific site downs tream from the major late promoter of adenovirus, Consistent with the model for transcription-coupled repair, an aminofluorene adduct locate d on the transcribed strand was a weak pause site for RNA polymerase I I, An acetylaminofluorene adduct located on the transcribed strand was an absolute block to transcriptional elongation, Either adduct locate d on the nontranscribed strand enhanced polymerase arrest at a nearby sequence specific pause site.