UBE2R1 is important in the control of cell cycle and DNA replication. In association with different E3 complexes, including SCF, it has been shown to target many different substrates for ubiquitination and degradation during cell division, signal transduction, and development. UBE2R1 substrates include B-Myb, Wee1, MyoD, ATF5, p27Xic1, and p27Kip1. Additionally, substrates such as p21Cip1, E2F, cyclin E, and cyclin D are putative substrates of UBE2R1 by virtue of their SCF requirement for proteolysis. This protein is useful for in vitro ubiquitinylation reactions.