The eukaryotic cell cycle is governed by cyclin-dependent protein kinases (CDKs) whose activities are regulated by cyclins and CDK inhibitors. Cyclin G1 encoded by CCNG1 is a member of the cyclin family and contains the cyclin box. The encoded protein lacks the protein destabilizing (PEST) sequence that is present in other family members. Transcriptional activation of CCNG1 can be induced by tumor protein p53. Two transcript variants encoding the same protein have been identified for CCNG1.