PWWP domain-containing DNA repair factor 3A (also known as EXPAND1 or MUM1) is a nucleosome-binding protein that contributes to the maintenance of chromatin state. Through its interaction with 53BP1, it serves as an accessory factor in the DNA damage response pathway to promote chromatin change in response to DNA damage [1]. MUM1 promotes cell survival following DNA damage, suggesting that it may facilitate DNA repair by regulating the organisation of chromatin structure [2]. This is the N-terminal domain from PWWP domain-containing DNA repair factors 3A/B, which shows similarities to chromodomains and may function as a histone reader.

1: Regulation of chromatin architecture by the PWWP domain-containing DNA damage-responsive factor EXPAND1/MUM1. Huen MS, Huang J, Leung JW, Sy SM, Leung KM, Ching YP, Tsao SW, Chen J; Mol Cell. 2010;37:854-864. PMID:20347427

2: The 53BP1-EXPAND1 connection in chromatin structure regulation. Sy SM, Chen J, Huen MS; Nucleus. 2010;1:472-474. PMID:21327088