The T-T pyrimidine (6-4) pyrimidinone UV photoproduct is much less mutagenic in yeast than in Escherichia coli.
We have examined the mutagenic properties of the T-T pyrimidine (6-4) pyrimidinone UV photoproduct in Saccharomyces cerevisiae, transforming the yeast cells either with single-stranded vectors that carried this adduct at a unique site or with gapped duplex vectors in which the adduct was located within a 28 nt single-stranded region. In an earlier study with SOS-induced Escherichia coli, we found that this photoproduct is highly mutagenic, specifically generating 3' T-->C substitutions in >85% of replicated molecules, and ascribed this specificity to the formation of a stable guanine-pyrimidinone mispair via hydrogen bonds at N-3 and O-2. In contrast, this adduct is very much less mutagenic in yeast, with 60-70% of molecules being replicated accurately and only 12-20% of them exhibiting 3' T-->C substitutions. The enhanced accuracy may reflect the ability of a yeast DNA polymerase, but not E.coli DNA polymerase III, to trap the adduct in a configuration favorable for the formation of an adenine-pyrimidinone base pair.
Gibbs
P E
PE
Department of Biophysics, University of Rochester School of Medicine and Dentistry, NY 14642, USA.
Borden
A
A
Lawrence
C W
CW
D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D015966:Gene Expression Regulation, Fungal; D016296:Mutagenesis; D011740:Pyrimidine Dimers / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism
D011740:Pyrimidine Dimers; C058406:pyrimidine-pyrimidone dimer