該基因編碼的蛋白質屬于高度保守的細胞周期蛋白家族，其成員在整個細胞周期內具有顯著的蛋白質豐度周期性。細胞周期蛋白起著調節CDK激酶的作用。不同的細胞周期蛋白表現出不同的表達和降解模式，這有助于每個有絲分裂事件的時間協調。該細胞周期蛋白與CDK4或CDK6形成復合物并作為其調節亞單位發揮作用，其活性是細胞周期G1/S轉換所必需的。該蛋白與腫瘤抑制蛋白Rb相互作用，該基因的表達受到Rb的正調控。這種基因的突變、擴增和過度表達改變了細胞周期的進程，在多種腫瘤中經常觀察到，并可能有助于腫瘤的發生。
The protein encoded by this gene belongs to the highly conserved cyclin family, whose members are characterized by a dramatic periodicity in protein abundance throughout the cell cycle. Cyclins function as regulators of CDK kinases. Different cyclins exhibit distinct expression and degradation patterns which contribute to the temporal coordination of each mitotic event. This cyclin forms a complex with and functions as a regulatory subunit of CDK4 or CDK6, whose activity is required for cell cycle G1/S transition. This protein has been shown to interact with tumor suppressor protein Rb and the expression of this gene is regulated positively by Rb. Mutations, amplification and overexpression of this gene, which alters cell cycle progression, are observed frequently in a variety of tumors and may contribute to tumorigenesis.