Cyclin B1 Interacting Protein 1 (CCNB1IP1)

HEI10 is a member of the E3 ubiquitin ligase family and functions in progression of the cell cycle through G(2)/M. HEI10 expression in Xenopus oocytes showed that HEI10 acts as an E3 ubiquitin ligase, causing delayed entry into mitosis by reducing cyclin B levels. In vitro, the cyclin B-cdc2 complex phosphorylated HEI10 primarily at the NTPVR cell cycle kinase consensus site.

The protein contains a divergent RING finger motif in the N terminus, a coiled-coil domain, and cyclin and cyclin-dependent kinase phosphorylation sites in the C terminus. Northern blot analysis identified a 1.6-kb HEI10 transcript that was expressed at high levels in heart, moderate levels in kidney and liver, and low levels in placenta, brain, and lung.