Polymerase δ promotes chromosomal rearrangements and imprecise double-strand break repair

Abstract

Recent studies have implicated DNA polymerases θ (Pol θ) and β (Pol β) as mediators of alternative nonhomologous end-joining (Alt-NHEJ) events, including chromosomal translocations. Here we identify subunits of the replicative DNA polymerase δ (Pol δ) as promoters of Alt-NHEJ that results in more extensive intrachromosomal mutations at a single double-strand break (DSB) and more frequent translocations between two DSBs. Depletion of the Pol δ accessory subunit POLD2 destabilizes the complex, resulting in degradation of both POLD1 and POLD3 in human cells. POLD2 depletion markedly reduces the frequency of translocations with sequence modifications but does not affect the frequency of translocations with exact joins. Using separation-of-function mutants, we show that both the DNA synthesis and exonuclease activities of the POLD1 subunit contribute to translocations. As described in yeast and unlike Pol θ, Pol δ also promotes homology-directed repair. Codepletion of POLD2 with 53BP1 nearly eliminates translocations. POLD1 and POLD2 each colocalize with phosphorylated H2AX at ionizing radiation-induced DSBs but not with 53BP1. Codepletion of POLD2 with either ligase 3 (LIG3) or ligase 4 (LIG4) does not further reduce translocation frequency compared to POLD2 depletion alone. Together, these data support a model in which Pol δ promotes Alt-NHEJ in human cells at DSBs, including translocations.

Multifaceted Nature of DNA Polymerase θ

“…The DNA synthesis step is apparently not restricted to Pol θ; the high-fidelity replicative DNA polymerase Pol δ may be involved both in yeast and mammals [ 41 , 42 ]. It has been also hypothesized that, due to insufficient processivity, Pol θ only initiates synthesis from annealed microhomologies, and, subsequently, Pol δ fills the gap.…”

Underappreciated Roles of DNA Polymerase δ in Replication Stress Survival

“…On the basis of these findings, the authors proposed that BIR mediated by POLD3 at compromised replication forks accounts in part for short-range genomic duplications in human cancers. Finally, Pol δ can promote intra-and interchromosomal translocations through alternative NHEJ (nonhomologous end joining), thereby further contributing to potentially oncogenic genome alterations [61].…”

Identification of key molecules in COVID-19 patients significantly correlated with clinical outcomes by analyzing transcriptomic data

“…The coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has caused nearly 477 million cases and more than 6 million deaths as of March 25, 2022 ( 1 ). Moreover, the number of COVID-19 cases have been dramatically increasing since the virus has evolved to higher infectivity, such as the Omicron variant ( 2 ).…”