A complex of BRCA2 and PP2A-B56 is required for DNA repair by homologous recombination

Sara M Ambjørn,Thomas Van Overeem Hansen,Blanca Lopez-Mendez,Jakob Nilsson,Vibe H Oestergaard,Isha Nasa,Beata Rymarczyk,Julien P Duxin,Michael Lisby,Lauren E Cressey,Thomas Kruse,Emil P T Hertz,Arminja N Kettenbach,Joana Duro

doi:10.1038/s41467-021-26079-0

Abstract

Mutations in the tumour suppressor gene BRCA2 are associated with predisposition to breast and ovarian cancers. BRCA2 has a central role in maintaining genome integrity by facilitating the repair of toxic DNA double-strand breaks (DSBs) by homologous recombination (HR). BRCA2 acts by controlling RAD51 nucleoprotein filament formation on resected single-stranded DNA, but how BRCA2 activity is regulated during HR is not fully understood. Here, we delineate a pathway where ATM and ATR kinases phosphorylate a highly conserved region in BRCA2 in response to DSBs. These phosphorylations stimulate the binding of the protein phosphatase PP2A-B56 to BRCA2 through a conserved binding motif. We show that the phosphorylation-dependent formation of the BRCA2-PP2A-B56 complex is required for efficient RAD51 filament formation at sites of DNA damage and HR-mediated DNA repair. Moreover, we find that several cancer-associated mutations in BRCA2 deregulate the BRCA2-PP2A-B56 interaction and sensitize cells to PARP inhibition. Collectively, our work uncovers PP2A-B56 as a positive regulator of BRCA2 function in HR with clinical implications for BRCA2 and PP2A-B56 mutated cancers.

Highlights

Mutations in the tumour suppressor gene BRCA2 are associated with predisposition to breast and ovarian cancers
We previously identified a putative binding motif for the serine/ threonine protein phosphatase PP2A-B56 in BRCA2, which is of unknown significance[20]
The LxxIxE motif in BRCA2 is embedded in a hitherto uncharacterized region between BRC repeat 1 and 2 comprising residues 1102–1132, which is highly conserved spanning more than 450 million years of evolution (190 fulllength vertebrate BRCA2 protein sequences analyzed by Clustal Omega multiple sequence alignment) (Fig.1b and Supplementary Data 1)

Summary

Introduction

Mutations in the tumour suppressor gene BRCA2 are associated with predisposition to breast and ovarian cancers. BRCA2 has a central role in maintaining genome integrity by facilitating the repair of toxic DNA double-strand breaks (DSBs) by homologous recombination (HR). BRCA2 acts by controlling RAD51 nucleoprotein filament formation on resected singlestranded DNA, but how BRCA2 activity is regulated during HR is not fully understood. We show that the phosphorylation-dependent formation of the BRCA2-PP2A-B56 complex is required for efficient RAD51 filament formation at sites of DNA damage and HR-mediated DNA repair. Homologous recombination (HR) is an essential cellular process that repairs severe DNA lesions such as DNA double-strand breaks (DSBs) to ensure genome integrity[1]. BRCA2 plays a central role in HR by controlling the formation of RAD51 nucleoprotein filaments on resected RPA-coated single-stranded DNA ends, which can search for and invade a homologous repair template[4,5,6]. Recent discoveries of consensus binding motifs for protein phosphatases[19,20,21] allows for precise dissection of their roles in DNA repair processes

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