Mutagenesis in eukaryotes dependent on DNA polymerase zeta and Rev1p

Abstract

DNA polymerase zeta (Pol z) and Rev1p carry out translesion replication in budding yeast, Saccharomyces cerevisiae, and are jointly responsible for almost all base pair substitution and frameshift mutations induced by DNA damage in this organism. In addition, Pol z is responsible for the majority of spontaneous mutations in yeast and has been proposed as the enzyme responsible for somatic hypermutability. Pol z, a non-processive enzyme that lacks a 3' to 5' exonuclease proofreading activity, is composed of Rev3p, the catalytic subunit, and a second subunit encoded by REV7. In keeping with its role, extension by Pol z is relatively tolerant of abnormal DNA structure at the primer terminus and is much more capable of extension from terminal mismatches than yeast DNA polymerase alpha (Pol a). Rev1p is a bifunctional enzyme that possesses a deoxycytidyl transferase activity that incorporates deoxycytidyl opposite abasic sites in the template and a second, at present poorly de¢ned, activity that is required for the bypass of a variety of lesions as well as abasic sites. Human homologues of the yeast REV1 and REV3 have been identi¢ed and, based on the phenotype of cells producing antisense RNA to one or other of these genes, their products appear also to be employed in translation replication and spontaneous mutagenesis. We suggest that Pol z is best regarded as a replication enzyme, albeit one that is used only intermittently, that promotes extension at forks the progress of which is blocked for any reason, whether the presence of an unedited terminal mismatch or unrepaired DNA lesion.

DNA polymerase zeta (pol ζ) in higher eukaryotes

“…A screen for mutants conferring a "reversionless" phenotype (identifying cells with reduced UV radiation-induced mutagenesis) revealed a set of genes including REV1 and REV3. An intensive investigation by C Lawrence's group [4,7] of these mutant genes was undertaken, and the additional gene REV7 was www.cell-research.com | Cell Research Gregory N Gan et al 175 npg discovered [8]. A critical advance was the demonstration that S. cerevisiae DNA pol ζ consists of a core of two subunits: Rev3, the catalytic polymerase subunit, and Rev7, an accessory protein which enhanced the catalytic activity of the polymerase [9].…”

“…Most present information about the biochemistry of pol ζ comes from studies using the budding yeast S. cerevisiae [1][2][3][4]. An early identification of genes associated with UV-induced mutagenesis came from studies of J Lemontt, working in R Mortimer's group [5,6].…”

“…The most striking consequence of the absence of Rev3 in budding yeast is, however, the large reduction (by 90% or more) in the frequency of base pair substitution and frameshift mutations induced by UV radiation. Mutagenesis by g-rays and methylmethane sulfonate is also lowered in rev3 mutants [4,10,13], and the frequency of spontaneous point mutations is reduced by at least half [14][15][16]. Spontaneous mutation in S. cerevisiae is proportional to transcription level at some loci, and this transcription-associated mutagenesis is also Rev3-dependent [17].…”

Analysis of Rev1p and Pol ζ in mitochondrial mutagenesis suggests an alternative pathway of damage tolerance

“…Rev1p and Pol ζ are responsible for the majority of UV-induced nuclear frameshift mutations [25]. Pol ζ is also responsible for essentially all the spontaneous nuclear frameshift mutations [25].…”

“…Pol ζ is also responsible for essentially all the spontaneous nuclear frameshift mutations [25]. Therefore, we analyzed the effect of deleting Pol ζ and Rev1p on mitochondrial frameshifts in microsatellite tracts.…”