cyclin box found in Saccharomyces cerevisiae G1/S-specific cyclin PCL1, PCL2 and similar proteins
The family includes a group of cyclin-like proteins that interact with the Pho85 cyclin-dependent kinase, such as Saccharomyces cerevisiae G1/S-specific cyclin PCL1, PCL2, PCL9 and their vertebrate counterparts, cyclin Pas1/PHO80 domain-containing protein 1 (CNPPD1). PCL1 (also called PHO85 cyclin-1, or cyclin HCS26) and PCL2 (also called PHO85 cyclin-1, or cyclin HCS26 homolog) are G1/S-specific cyclin partners of the cyclin-dependent kinase (CDK) PHO85. They are essential for the control of the cell cycle at the G1/S (start) transition. The PCL1-PHO85 cyclin-CDK holoenzyme is involved in phosphorylation of the CDK inhibitor (CKI) SIC1, which is required for its ubiquitination and degradation, releasing repression of b-type cyclins and promoting exit from mitosis. Together with cyclin PCL2, it positively controls degradation of sphingoid long chain base kinase LCB4. PCL1-PHO85 also phosphorylates HMS1, NCP1 and NPA3, which may all have a role in mitotic exit. PCL2-PHO85 also phosphorylates RVS167, linking cyclin-CDK activity with organization of the actin cytoskeleton. PCL9 is an M/G1-specific cyclin partner of the cyclin-dependent kinase (CDK) PHO85. It may have a role in bud site selection in the G1 phase. The family also includes cyclin Pas1/PHO80 domain-containing protein 1 (CNPPD1) and similar proteins. Their biological functions remain unclear. Members of this family contain one cyclin box. The cyclin box is a protein binding domain.