REV7 is required for processing AID initiated DNA lesions in activated B cells

Dingpeng Yang,Shuangshuang Fan,Liming Sun,Jingjing Chen,Ying Sun,Leng-Siew Yeap,Tuantuan Gui,Xia Xie,Xiaoming Wang,Yanni Cai,Min Huang,Ying Zhang,Yafang Shang,Fei-Long Meng,Jiazhi Hu,Wei Xiao,Junchao Dong

doi:10.1038/s41467-020-16632-8

Abstract

Activation-induced cytidine deaminase (AID) initiates both antibody class switch recombination (CSR) and somatic hypermutation (SHM) in antibody diversification. DNA double-strand break response (DSBR) factors promote rearrangement in CSR, while translesion synthesis (TLS) polymerases generate mutations in SHM. REV7, a component of TLS polymerase zeta, is also a downstream effector of 53BP1-RIF1 DSBR pathway. Here, we study the multi-functions of REV7 and find that REV7 is required for the B cell survival upon AID-deamination, which is independent of its roles in DSBR, G2/M transition or REV1-mediated TLS. The cell death in REV7-deficient activated B cells can be fully rescued by AID-deficiency in vivo. We further identify that REV7-depedent TLS across UNG-processed apurinic/apyrimidinic sites is required for cell survival upon AID/APOBEC deamination. This study dissects the multiple roles of Rev7 in antibody diversification, and discovers that TLS is not only required for sequence diversification but also B cell survival upon AID-initiated lesions.

Highlights

Activation-induced cytidine deaminase (AID) initiates both antibody class switch recombination (CSR) and somatic hypermutation (SHM) in antibody diversification
Similar reduction of CSR-activated REV7-deficient B cells was observed in both cell number counting and cytometry assays upon LPS plus IL4 or LPS stimulation (Supplementary Fig. 1g, h), except less apoptotic REV7-deficient B-cell population was observed upon LPS plus IL4 stimulation, potentially reflecting a role of IL4-initiated anti-apoptotic single transduction pathway[41]
We report that multiple roles of REV7 are required to process AID-initiated DNA lesions in CSR-activated B cells ex vivo and germinal center (GC) B cells in vivo

Summary

Introduction

Activation-induced cytidine deaminase (AID) initiates both antibody class switch recombination (CSR) and somatic hypermutation (SHM) in antibody diversification. DNA doublestrand break response (DSBR) factors promote rearrangement in CSR, while translesion synthesis (TLS) polymerases generate mutations in SHM. We further identify that REV7-depedent TLS across UNG-processed apurinic/apyrimidinic sites is required for cell survival upon AID/APOBEC deamination. This study dissects the multiple roles of Rev[7] in antibody diversification, and discovers that TLS is required for sequence diversification and B cell survival upon AID-initiated lesions. Mature B cells can undergo antibody diversification processes including immunoglobulin heavy chain (IgH) class switch recombination (CSR) and variable (V) exon somatic hypermutation (SHM)[1]. Various DNA repair pathways function downstream and channel the deamination products into double-strand breaks (DSBs), mutations, or small insertions/deletions (indels). Deletion of either factor in this pathway results in decreased CSR level in various mouse models[8,9,10]

Methods

Results

Conclusion