MMS1 is a protein that protects against replication-dependent DNA damage in Saccharomyces cerevisiae. MMS1 belongs to the DDB1 family of cullin 4 adaptors and the two proteins are homologous. MMS1 bridges the interaction of MMS22 and Crt10 with Cul8/Rtt101. Cul8/Rtt101 is a cullin protein involved in the regulation of DNA replication subsequent to DNA damage. The N-terminal region of MMS1 and the C-terminal of MMS22 are required for the the MMS1-MMS22 interaction. The human HIV-1 virion-associated protein Vpr assembles with DDB1 through interaction with DCAF1 (chromatin assembly factor) to form an E3 ubiquitin ligase that targets cellular substrates for proteasome-mediated degradation and subsequent G2 arrest.