G1/S-specific cyclin partner of the cyclin-dependent kinase (CDK) PHO85. 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, positively controls degradation of sphingoid long chain base kinase LCB4. PCL1-PHO85 phosphorylates LCB4, which is required for its ubiquitination and degradation. PCL1-PHO85 also phosphorylates HMS1, NCP1 and NPA3, which may all have a role in mitotic exit. Forms a cyclin-CDK complex with PHO85 (PubMed:7973730, PubMed:9032248). Interacts with HMS1, NCP1 and NPA3 (PubMed:15082539, PubMed:9032248). Interacts with DMA1 (PubMed:23264631). Localizes to the incipient bud site. By transcription factor SBF (SWI4-SWI6 cell-cycle box binding factor) in a cell cycle-regulated manner. Peaks in G1 phase. Phosphorylated by PHO85; necessary for interaction with DMA1 and subsequent degradation. Ubiquitinated by E3 ubiquitin ligase DMA1 in response to nutrient condition; this targets PCL1 for destruction. Present with 606 molecules/cell in log phase SD medium. Belongs to the cyclin family. PCL1,2 subfamily.