XRCC1 Prevents Toxic PARP1 Trapping During DNA Base Excision Repair

Annie A Demin,Kouji Hirota,Masataka Tsuda,William Gittens,Keith W Caldecott,Hiroyuki Sasanma,Shunichi Takeda,Hana Hanzlikova,Richard Hailstone,Marek Adamowicz,Jan Brazina

doi:10.2139/ssrn.3749695

Annie A Demin, Kouji Hirota + Show 9 more

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https://doi.org/10.2139/ssrn.3749695

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Abstract

Mammalian DNA base excision repair (BER) is an essential pathway comprised of damaged base excision by a DNA glycosylase, incision by AP endonuclease-1 (APE1), end processing and gap filling by DNA polymerase β (POLβ), and DNA ligation by DNA ligase I (LIG1) or DNA ligase III (LIG3). In mammals, BER additionally employs PARP1 and/or PARP2 and the scaffold protein XRCC1 to accelerate and coordinate the overall process. Whereas PARP1 and PARP2 are sensor proteins that detect unrepaired DNA single-strand breaks, the essential role of XRCC1 during BER is unknown. Here, we have identified this role. We show that the DNA repair protein complexes that are assembled by XRCC1 compete with and prevent excessive PARP1 engagement during BER, which otherwise leads to PARP1 ‘trapping’ on BER intermediates in a manner reminiscent of that induced by clinical PARP inhibitors. We demonstrate that this elevated engagement and trapping of PARP1 collectively renders BER intermediates inaccessible to POLβ and impedes their repair. Consequently, PARP1 deletion rescues both the accessibility and repair of BER intermediates in XRCC1-/- cells, and also their cellular resistance to DNA base damage. These data demonstrate that PARP1 trapping is an endogenous threat to genome integrity, and identify XRCC1 as an “anti-trapper” that prevents the toxic binding of PARP1 to BER intermediates to ensure their efficient repair.

Highlights

DNA base excision repair (BER) is a highly conserved pathway that is present in all organisms and required for repair of a broad range of endogenous and exogenous DNA base damage (Beard et al., 2019; Caldecott, 2020)
We show that assembly of polymerase b (POLb) and LIG3 by XRCC1 into protein complexes is required to limit poly(ADP-ribose) polymerase-1 (PARP1) engagement and activity during BER, which otherwise results in PARP1 ‘‘trapping’’ on BER intermediates in a manner reminiscent of that induced by clinical poly(ADP-ribose) polymerases (PARPs) inhibitors
To address the role of XRCC1 during BER, we first examined its functional relationship with PARP1 because the ability of XRCC1 to interact directly with poly(ADP-ribose) is critical for this role (Breslin et al, 2015)

Summary

Introduction

DNA base excision repair (BER) is a highly conserved pathway that is present in all organisms and required for repair of a broad range of endogenous and exogenous DNA base damage (Beard et al., 2019; Caldecott, 2020). The canonical BER pathway involves removal of the damaged base by a DNA glycosylase, incision of the resulting abasic site by AP endonuclease In addition to these core components, mammalian cells employ a number of additional proteins to accelerate BER, such as poly(ADP-ribose) polymerase-1 (PARP1), PARP2, and the molecular scaffold protein XRCC1 (Caldecott et al, 1994; Dantzer et al, 1999; Ding et al, 1992; Page et al., 2003; Ronson et al, 2018; Schreiber et al, 2002; Thompson et al, 1990). PARP1 and PARP2 are sensor proteins that detect and are activated by DNA strand breaks, resulting in the posttranslational modification of themselves and other proteins with.

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