Transcription elongation factor S-II maintains transcriptional fidelity and confers oxidative stress resistance.
BACKGROUND
During transcription elongation, RNA polymerase II is arrested on the template when incorrect ribonucleotides are incorporated into the nascent transcripts. Transcription factor S-II enhances the excision of these mis-incorporated nucleotides by RNA polymerase II and stimulates transcription elongation in vitro. This mechanism is considered to be transcriptional proof-reading, but its physiological relevance remains unknown.


RESULTS
We report that S-II contributes to the maintenance of transcriptional fidelity in vivo. We employed a genetic reporter assay utilizing a mutated lacZ gene from which active beta-galactosidase protein is expressed when mRNA proof-reading is compromised. In S-II-disrupted mutant yeasts, beta-galactosidase activity was ninefold higher than that in wild-type. The S-II mutant exhibited sensitivity to oxidants, which was suppressed by introduction of the S-II gene. The mutant S-II proteins, which are unable to stimulate transcription by RNA polymerase II in vitro, did not suppress the sensitivity of the mutants to oxidative stress or maintain transcriptional fidelity.


CONCLUSIONS
These results suggest that S-II confers oxidative stress resistance by providing an mRNA proof-reading mechanism during transcription elongation.
Koyama
Hiroshi
H
Department of Developmental Biochemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Ito
Takahiro
T
Nakanishi
Toshiyuki
T
Kawamura
Nobuyuki
N
Sekimizu
Kazuhisa
K
D000111:Acetylcysteine / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D015966:Gene Expression Regulation, Fungal / Q000235:genetics*; D005800:Genes, Fungal; D017930:Genes, Reporter; D007763:Lac Operon / Q000235:genetics; D009154:Mutation; D009876:Operon / Q000235:genetics; D016877:Oxidants / Q000378:metabolism; D018384:Oxidative Stress; D012319:RNA Polymerase II / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000378:metabolism
D000975:Antioxidants; D016877:Oxidants; D014157:Transcription Factors; D012319:RNA Polymerase II; D001616:beta-Galactosidase; D000111:Acetylcysteine