Y-family DNA polymerases in mammalian cells

Abstract

Eukaryotic genomes are replicated with high fidelity to assure the faithful transmission of genetic information from one generation to the next. The accuracy of replication relies heavily on the ability of replicative DNA polymerases to efficiently select correct nucleotides for the polymerization reaction and, using their intrinsic exonuclease activities, to excise mistakenly incorporated nucleotides. Cells also possess a variety of specialized DNA polymerases that, by a process called translesion DNA synthesis (TLS), help overcome replication blocks when unrepaired DNA lesions stall the replication machinery. This review considers the properties of the Y-family (a subset of specialized DNA polymerases) and their roles in modulating spontaneous and genotoxic-induced mutations in mammals. We also review recent insights into the molecular mechanisms that regulate PCNA monoubiquitination and DNA polymerase switching during TLS and discuss the potential of using Y-family DNA polymerases as novel targets for cancer prevention and therapy.

DNA damage tolerance pathway involving DNA polymerase ι and the tumor suppressor p53 regulates DNA replication fork progression

“…7). Notably, our work elucidates a new role of p53(WT), together with POLι, an extremely errorprone and highly enigmatic POL in humans (59) without paralogs in bacteria, yeast, or nematodes (48).…”

“…Bars indicate SEM. Because TLS-POLs are recruited to replication sites by PCNA ubiquitination (48), and because we observed an epistatic relationship between POLι and p53(WT) in our screening, the possibility of an interaction between p53(WT) and POLι was evaluated. PLA and POLι coimmunoprecipitation (Fig.…”

“…We noticed complete dependency of p53-mediated recombination with one specific TLS-POL, namely POLι. The observed moderate influences of TLS-POLκ and the TLS-POLζ catalytic subunit REV3L could be explained by functional overlap and cooperation with TLS-POLι, respectively (48,68). Because p53(WT), but not p53(H115N), facilitated the accumulation of POLι-foci and, conversely, POLι silencing impaired accumulation of p53pSer15 foci in cross-linker-treated cells expressing exonuclease-proficient p53, we propose exonuclease-dependent stabilization of a p53-POLι complex at replication lesions.…”

“…The latter can further be subdivided into strand invasion or fork reversal mechanisms (36,60). The stimulation of recombination by p53(WT) was fully epistatic with the E3-ubiquitin ligase RAD18, which monoubiquitinates PCNA in conjunction with the E2-conjugating enzyme RAD6 (60), and with POLι, which recognizes monoubiquitinated PCNA (48). Intriguingly, it has previously been speculated that p53 is required for efficient, UV-induced PCNA monoubiquitination (39,61).…”

Bypass of Mutagenic O6-Carboxymethylguanine DNA Adducts by Human Y- and B-Family Polymerases

“…In this process, TLS Pols are deployed to overcome blockages, protecting cells from acute toxicity however at the possible cost of base misincorporation and genomic instability. [40][41][42][43] The potential for base misincorporation during DNA replication by a variety of human Pols in bypassing O 6 -alkylG adducts has been described; 24 however the presence of O 6 -CMG in the template has never been examined for human Y-and B-family polymerases. Herein, we examined the chemical basis of this process by characterizing the propensity of four human TLS Pols, Pol η, κ, ι and ζ vs the replicative Pol δ, to catalyze the bypass and extension past an O 6 -CMG adduct with primer extension and steady-state kinetics studies.…”