Canadian Medical Guide > Chemicals and Drugs > Growth Substances, Pigments, and Vitamins > Growth Substances > Cyclins Terms and Definitions

Cyclins

Medical Definition:	Regulatory proteins that function in the cell cycle to activate maturation promoting factor. They complex with p34cdc2 (PROTEIN P34CDC2), the catalytic subunit of MATURATION-PROMOTING FACTOR, and modulate its protein kinase activity. Cyclins themselves have no enzymatic activity.
Guide Notes:	regulatory proteins; growth substances; do not confuse with the nuclear protein cyclin (PCNA or Proliferating Cell Nuclear Antigen); note specifics
Previously Indexed:	Invertebrate Hormones (1987-1990)

Cyclins Categories.

	Cyclin A - A 33-kD protein identical to adenovirus E1A-associated protein p60. Cyclin A regulates p33cdk2 and p34cdc2, and is necessary for progression through the S phase of the cell cycle.
	Cyclin B - A 58-kD protein that is regulated post-transcriptionally and post-translationally in the cell cycle.
	Cyclin D1 - Protein encoded by the bcl-1 gene which plays a critical role in regulating the cell cycle. Overexpression of cyclin D1 is the result of bcl-1 rearrangement, a t(11;14) translocation, and is implicated in various neoplasms.
	Cyclin E - A 50-kD protein that complexes with cdk2 in the late G1 phase of the cell cycle.

Cyclins Medical Definitions and Terms

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