Ubiquitin-dependent degradation of Cyclin D

Ubiquitin-dependent degradation of Cyclin D Cyclin D turnover is regulated by ubiquitination and proteasomal degradation which are positively regulated by cyclin D phosphorylation on threonine-286 (Diehl et al., 1997).After the Cyclin D serves the role of mediating reactions by Cdk4 and Cdk6, it is shuttled to the cytoplasm and degraded in a ubiquitin-dependent manner. Whether Cdk4 and Cdk6 are truly redundant is a topic still under investigation, although both the kinases are required for normal cell cycle progression.Destruction of the D type cyclins accompanies the end of the G1 phase, and the E type cyclins are involved in transition of the cell from G1 to S phase.