PrimPol prevents APOBEC/AID family mediated DNA mutagenesis

Abstract

PrimPol is a DNA damage tolerant polymerase displaying both translesion synthesis (TLS) and (re)-priming properties. This led us to study the consequences of a PrimPol deficiency in tolerating mutagenic lesions induced by members of the APOBEC/AID family of cytosine deaminases. Interestingly, during somatic hypermutation, PrimPol counteracts the generation of C>G transversions on the leading strand. Independently, mutation analyses in human invasive breast cancer confirmed a pro-mutagenic activity of APOBEC3B and revealed a genome-wide anti-mutagenic activity of PRIMPOL as well as most Y-family TLS polymerases. PRIMPOL especially prevents APOBEC3B targeted cytosine mutations within TpC dinucleotides. As C transversions induced by APOBEC/AID family members depend on the formation of AP-sites, we propose that PrimPol reprimes preferentially downstream of AP-sites on the leading strand, to prohibit error-prone TLS and simultaneously stimulate error-free homology directed repair. These in vivo studies are the first demonstrating a critical anti-mutagenic activity of PrimPol in genome maintenance.

DNA damage tolerance in hematopoietic stem and progenitor cells in mice

“…PCNA K164-independent mechanisms of TLS recruitment (e.g., the Y-family TLS polymerase REV1) can recruit other Y-family TLS polymerases to stalled forks (25)(26)(27)(28). In Saccharomyces cerevisiae, a DDT-independent role of PCNA K164 modification has been suggested to play a minor role in lagging strand synthesis under unperturbed conditions (29), although that study could not exclude differential DDT activity on the leading vs. lagging strand in response to endogenous DNA damage and replication blocking lesions (19). In mammals, TLS is the predominant pathway, and PCNA-Ub-mediated TLS can be readily observed on DNA damage induction, whereas PCNAUb n -mediated TS seems less frequent (30,31).…”

“…B and T development. The lymphocyte composition and precursor subsets in thymus and bone marrow were analyzed as described previously (19). In vivo EdU incorporation assay.…”

“…However, these replicative polymerases can be stalled by replication blocks, such as DNA lesions, G4 stacks, ribonucleotide misincorporation, and RNA/DNA hybrids that persist into or arise during S phase (16)(17)(18). To bypass such replication blocking lesions or structures and prevent secondary DNA damage due to prolonged fork stalling, three principle modes of DNA damage tolerance (DDT) are distinguished: translesion synthesis (TLS), template switching (TS), and repriming (19)(20)(21)(22)(23). PCNA K164-specific modifications are key to the ability to efficiently switch between a replicative mode and a damagetolerant mode of DNA replication.…”

DNA polymerases in the mitochondria A critical review of the evidence

“…Translesion synthesis by PrimPol is particularly error prone yet transient, as it has been shown the PrimPol incorporates only 4 bp on average per binding event (55, 57). However, while TLS conducted by PrimPol is highly mutagenic (57), PrimPol repriming events downstream of an AP site, particularly those created an APOBEC/AID family protein, leads to error-free resumption of replication, resulting in an overall anti-mutagenic effect (58). Taken together, these unique roles indicate an important role for PrimPol in maintenance of nuclear and potentially mitochondrial DNA.…”

Starting over: Primpol reprimes after chain termination

“…Given the apparently crucial function PrimPol fulfils during replication, and the broad range of impediments at which it can be deployed, it is somewhat surprising that cells lacking PrimPol, and indeed PrimPol-deficient mice, 7 are not more disabled. This is most likely explained by significant redundancy between PrimPol and alternative mechanisms that ensure that DNA replication is completed.…”