Transcriptional regulation of the cyclin D1 gene at a glance.

Regulated progression through the cell cycle requires sequential expression of a family of proteins called cyclins. Upon their induction, cyclins form complexes with specific cyclin-dependent kinases (CDKs), creating active holoenzymes that phosphorylate target proteins that are required for cell-cycle progression. Induction of the proto-oncogene cyclin D1, and its binding to CDK4 or CDK6, is a ratelimiting event during cell-cycle progression through G1 phase. Some studies suggest that cyclin D1 also has CDK-independent functions (reviewed by Fu et al., 2004).