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 entry represents the PWWP (named after the a conserved Pro-Trp-Trp-Pro motif), a small domain consisting of 100-150 amino acids, found in numerous proteins that are involved in cell division, growth and differentiation. Most PWWP-domain proteins seem to be nuclear, often DNA-binding proteins, that function as transcription factors regulating a variety of developmental processes [3].

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

3: The PWWP domain: a potential protein-protein interaction domain in nuclear proteins influencing differentiation?. Stec I, Nagl SB, van Ommen GJ, den Dunnen JT; FEBS Lett. 2000;473:1-5. PMID:10802047