Mechanism of genome instability mediated by human DNA polymerase mu misincorporation

Miao Guo,Jinfeng Hou,Yina Wang,Yuyue Tang,Liangyan Wang,Yuejin Hua,Jingli Dai,Ye Zhao,Bing Tian,Zijing Chen,Hong Xu,Yudong Wang

doi:10.1038/s41467-021-24096-7

Miao Guo, Jinfeng Hou + Show 10 more

Open Access

https://doi.org/10.1038/s41467-021-24096-7

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Journal: Nature Communications	Publication Date: Jun 18, 2021
Citations: 5	License type: open-access

Affiliation: Institute of Biophysics, Zhejiang University

Abstract

Pol μ is capable of performing gap-filling repair synthesis in the nonhomologous end joining (NHEJ) pathway. Together with DNA ligase, misincorporation of dGTP opposite the templating T by Pol μ results in a promutagenic T:G mispair, leading to genomic instability. Here, crystal structures and kinetics of Pol μ substituting dGTP for dATP on gapped DNA substrates containing templating T were determined and compared. Pol μ is highly mutagenic on a 2-nt gapped DNA substrate, with T:dGTP base pairing at the 3ʹ end of the gap. Two residues (Lys438 and Gln441) interact with T:dGTP and fine tune the active site microenvironments. The in-crystal misincorporation reaction of Pol μ revealed an unexpected second dGTP in the active site, suggesting its potential mutagenic role among human X family polymerases in NHEJ.

Highlights

Pol μ is capable of performing gap-filling repair synthesis in the nonhomologous end joining (NHEJ) pathway
While replicative DNA polymerases containing exonucleolytic proofreading activity are responsible for the normal DNA replication process, low-fidelity DNA polymerases concentrate on translesion[3], and repair synthesis[4] of damaged DNA bases; for example, Pol η5,6 and Pol β7,8 are well documented to be involved in bulky lesion bypass and base excision repair, respectively
Nonhomologous end joining (NHEJ) is the major repair pathway employed by higher eukaryotes to repair double-strand breaks (DSBs), which requires specialized DNA polymerases to bridge over DSB ends and fill small gaps prior to ligation[10]

Summary

Introduction

Pol μ is capable of performing gap-filling repair synthesis in the nonhomologous end joining (NHEJ) pathway. Pol μ containing an insertion in Loop[1] can fill small gapped DNA substrates[18,19,20,21], and a recent study revealed that Pol μ can effectively misinsert dGTP opposite 1-nt gapped DNA containing templating T22. This misincorporation further facilitates subsequent NHEJ ligation reaction by the DNA ligase IV/XRCC4 complex, which may lead to genomic instability during NHEJ repair

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