该基因编码的蛋白质属于高度保守的细胞周期蛋白家族，其成员在整个细胞周期内具有显著的蛋白质丰度周期性。细胞周期蛋白起着调节CDK激酶的作用。不同的细胞周期蛋白表现出不同的表达和降解模式，这有助于每个有丝分裂事件的时间协调。该细胞周期蛋白与CDK4或CDK6形成复合物并作为其调节亚单位发挥作用，其活性是细胞周期G1/S转换所必需的。该蛋白与肿瘤抑制蛋白Rb相互作用，该基因的表达受到Rb的正调控。这种基因的突变、扩增和过度表达改变了细胞周期的进程，在多种肿瘤中经常观察到，并可能有助于肿瘤的发生。
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.