Abstract: Cyclin E is expressed starting from the middle G1 phase of the cell cycle, and is accumulated in the G1/S boundry. Cyclin E binds to and activates the cyclindependent kinase CDK2. Cyclin E-CDK2 complex initiates a cascade of events that leads to DNA replication by phosphorylating its substrates, such as Rb, CDC6, NPAT and P107, etc. Additionally, cyclin E plays an important role in the regulation of genomic stability, spindleorganizing structure and centrosome cycle. Cyclin E expression is transactivated by members of the transcription factor E2F family and degrades via the ubiquitinproteasome pathway.  At the same time, it is also negatively regulated by the CIP/KIP proteins. Cyclin E highly expressed in the initiation and progression of different human cancers, such as breast cancers, lung cancers, leukemia, lymphomas and others.

Key words: Cyclin E, Cell cycle regulation, Cyclins, Neoplasms