This family contains repetitive element (RE) from a subgroup of HECT E3 ubiquitin ligases and the Y-family translesion polymerases, including human HUWE1 and Arabidopsis UPL1. Each of these repetitive elements are approximately 20 amino acids in length and contain two predicted helical segments separated by a Leu-Pro motif. The REs from the Y-family polymerases were shown to bind ubiquitin and were the basis for a novel ubiquitin-binding domain called the ubiquitin-binding motif (UBM) [1].

1: The UVS9 gene of Chlamydomonas encodes an XPG homolog with a new conserved domain. Deitsch E, Hibbard EM, Petersen JL; DNA Repair (Amst). 2016;37:33-42. PMID:26658142