A comprehensive collection of point mutations in the internal promoter of the adenoviral VAI gene.

Point mutations in the adenoviral VAI gene promoter were generated by in vitro mutagenesis with sodium bisulfite and were identified by three phenotypes: the disappearance of certain restriction endonuclease cleavage sites, altered rates of transcription in cell-free extracts, and altered mobility of the RNA product on denaturing acrylamide gels. 25 different point mutations were assayed for their effect on VAI transcription in HeLa S100 extracts. Mutations which change the transcriptional ability of the gene were localized in the internal control regions which are highly conserved among genes transcribed by RNA polymerase III. The magnitude of the change in transcription correlates with the degree of conservation in the consensus sequence at the site of the mutation. Most of the mutations either do not change the transcription rate or reduce transcription less than 6-fold. Two mutations severely reduce the amount of RNA produced, whereas three mutations increase the production of VAI RNA. A second site revertant that partially restores transcription to a mutant gene that produces no detectable VAI has also been isolated.