Pol31 and Pol32 subunits of yeast DNA polymerase ? are also essential subunits of DNA polymerase ?.

ABSTRACT: Replication through a diverse array of DNA lesions occurs by the sequential action of two translesion synthesis (TLS) DNA polymerases (Pols), in which one inserts the nucleotide opposite the lesion and the other carries out the subsequent extension. By extending from the nucleotide inserted by another Pol, Pol? plays an indispensable role in mediating lesion bypass. Pol? comprises the Rev3 catalytic and Rev7 accessory subunits. Pol32, a subunit of the replicative polymerase Pol?, is also required for Pol?-dependent TLS, but how this Pol? subunit contributes to Pol? function in TLS has remained unknown. Here we show that yeast Pol? is a four-subunit enzyme containing Rev3, Rev7, Pol31, and Pol32; in this complex, association with Pol31/Pol32 is mediated via binding of the Rev3 C terminus to Pol31. The functional requirement of this complex is supported by evidence that mutational inactivation of Rev3's ability to bind Pol31 abrogates Pol?'s role in TLS in yeast cells. These findings identify an unexpected role of Pol31 and Pol32 as two essential subunits of Pol?, and clarify why these proteins are required for Pol?-dependent TLS, but not for TLS mediated by Pol? in yeast cells. To distinguish the four-subunit complex from the two-subunit Pol?, we designate the four-subunit enzyme "Pol?-d," where "-d" denotes the Pol31/Pol32 subunits of Pol?.

SUBMITTER: Johnson RE 

PROVIDER: S-EPMC3411960 | biostudies-literature | 2012 Jul

REPOSITORIES: biostudies-literature