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PAXX binding to the NHEJ machinery explains functional redundancy with XLF.

Published version
Peer-reviewed

Repository DOI


Type

Article

Change log

Authors

Seif-El-Dahan, Murielle 
Kefala-Stavridi, Antonia 

Abstract

Nonhomologous end joining is a critical mechanism that repairs DNA double-strand breaks in human cells. In this work, we address the structural and functional role of the accessory protein PAXX [paralog of x-ray repair cross-complementing protein 4 (XRCC4) and XRCC4-like factor (XLF)] in this mechanism. Here, we report high-resolution cryo-electron microscopy (cryo-EM) and x-ray crystallography structures of the PAXX C-terminal Ku-binding motif bound to Ku70/80 and cryo-EM structures of PAXX bound to two alternate DNA-dependent protein kinase (DNA-PK) end-bridging dimers, mediated by either Ku80 or XLF. We identify residues critical for the Ku70/PAXX interaction in vitro and in cells. We demonstrate that PAXX and XLF can bind simultaneously to the Ku heterodimer and act as structural bridges in alternate forms of DNA-PK dimers. Last, we show that engagement of both proteins provides a complementary advantage for DNA end synapsis and end joining in cells.

Description

Keywords

Humans, Cryoelectron Microscopy, DNA, DNA End-Joining Repair, DNA Repair Enzymes

Journal Title

Sci Adv

Conference Name

Journal ISSN

2375-2548
2375-2548

Volume Title

9

Publisher

American Association for the Advancement of Science (AAAS)
Sponsorship
Wellcome Trust (200814/Z/16/Z)