title: A novel variant of DNA polymerase ζ, Rev3ΔC, highlights differential regulation of Pol32 as a subunit of polymerase δ versus ζ in Saccharomyces cerevisiae.
abstract: Unrepaired DNA lesions often stall replicative DNA polymerases and are bypassed by translesion synthesis (TLS) to prevent replication fork collapse. Mechanisms of TLS are lesion- and species-specific, with a prominent role of specialized DNA polymerases with relaxed active sites. After nucleotide(s) are incorporated across from the altered base(s), the aberrant primer termini are typically extended by DNA polymerase ζ (pol ζ). As a result, pol ζ is responsible for most DNA damage-induced mutations. The mechanisms of sequential DNA polymerase switches in vivo remain unclear. The major replicative DNA polymerase δ (pol δ) shares two accessory subunits, called Pol31/Pol32 in yeast, with pol ζ. Inclusion of Pol31/Pol32 in the pol δ/pol ζ holoenzymes requires a [4Fe-4S] cluster in C-termini of the catalytic subunits. Disruption of this cluster in Pol ζ or deletion of POL32 attenuates induced mutagenesis. Here we describe a novel mutation affecting the catalytic subunit of pol ζ, rev3ΔC, which provides insight into the regulation of pol switches. Strains with Rev3ΔC, lacking the entire C-terminal domain and therefore the platform for Pol31/Pol32 binding, are partially proficient in Pol32-dependent UV-induced mutagenesis. This suggests an additional role of Pol32 in TLS, beyond being a pol ζ subunit, related to pol δ. In search for members of this regulatory pathway, we examined the effects of Maintenance of Genome Stability 1 (Mgs1) protein on mutagenesis in the absence of Rev3-Pol31/Pol32 interaction. Mgs1 may compete with Pol32 for binding to PCNA. Mgs1 overproduction suppresses induced mutagenesis, but had no effect on UV-mutagenesis in the rev3ΔC strain, suggesting that Mgs1 exerts its inhibitory effect by acting specifically on Pol32 bound to pol ζ. The evidence for differential regulation of Pol32 in pol δ and pol ζ emphasizes the complexity of polymerase switches.
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA. Electronic address: hollie.siebler@unmc.edu.
authors.forename: Hollie M
authors.initials: HM
authors.lastname: Siebler
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA. Electronic address: alada@unmc.edu.
authors.forename: Artem G
authors.initials: AG
authors.lastname: Lada
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA. Electronic address: abaranovskiy@unmc.edu.
authors.forename: Andrey G
authors.initials: AG
authors.lastname: Baranovskiy
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA. Electronic address: ttahirov@unmc.edu.
authors.forename: Tahir H
authors.initials: TH
authors.lastname: Tahirov
authors.affiliation: Eppley Institute for Research in Cancer and Allied Diseases, 986805 Nebraska Medical Center, Omaha, NE 68198-6805, USA. Electronic address: ypavlov@unmc.edu.
authors.forename: Youri I
authors.initials: YI
authors.lastname: Pavlov
mesh_terms: D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004258:DNA Polymerase III / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D042822:Genomic Instability; D016296:Mutagenesis; D009154:Mutation; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination; D014466:Ultraviolet Rays; D000099270:Y-Family DNA Polymerases
chemical_list: D004265:DNA Helicases; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D009713:Nucleotidyltransferases; D018809:Proliferating Cell Nuclear Antigen; D029701:Saccharomyces cerevisiae Proteins; C522758:Pol32 protein, S cerevisiae; C425929:DNA polymerase zeta; C100951:REV1 protein, S cerevisiae; D000099270:Y-Family DNA Polymerases; C095943:POL31 protein, S cerevisiae; C092602:REV3 protein, S cerevisiae; C506739:MGS1 protein, S cerevisiae
keywords: Mgs1; Pol32; Polymerase switch; Polymerase ζ; Translesion DNA synthesis; UV mutagenesis