Cyclin-dependent kinase that acts as a master regulator of the mitotic and meiotic cell cycles (PubMed:8087848, PubMed:9042863, PubMed:1896017, PubMed:2274045, PubMed:6581157, PubMed:7498766, Ref.6). Required to drive the G1-S and G2-M transitions, and initiation of premeiotic DNA replication and meiosis II (PubMed:8087848, PubMed:9042863, PubMed:1896017, PubMed:2274045, PubMed:6581157, PubMed:7498766, Ref.6). More than 200 substrates have been identified (PubMed:27984725). Substrate specificity is in part regulated by the bound cyclin protein (PubMed:27984725). When complexed with cyclin cig2, it drives the G1-S phase transition (PubMed:8087848). When complexed with cyclin cdc13, it drives the G2-M transition and initiation of meiosis II (PubMed:8087848, PubMed:7498766). Its activity rises throughout the cell cycle and substrate specificity is further influenced by activity thresholds with more sensitive substrates phosphorylated earlier in the cell cycle than less sensitive substrates (PubMed:27984725). Phosphorylates dis1 during metaphase to ensure proper microtubule dynamics and accurate chromosome segregation (PubMed:16920624). Phosphorylates the repetitive C-terminus of the large subunit of RNA polymerase II rpb1 (Probable). Inactivated by checkpoint signaling following detection of cellular damage, leading to cell cycle arrest to allow damage repair (PubMed:9042863, PubMed:16049013). Inactivated during G2 DNA damage checkpoint signaling (PubMed:9042863). Inactivated in response to defective RNA splicing (PubMed:16049013). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Phosphorylation at Thr-14 or Tyr-15 inactivates the enzyme, while phosphorylation at Thr-167 activates it. Forms a stable but non-covalent complex with regulatory subunit suc1 and with a cyclin (PubMed:3322810). Interacts with cyclin cdc13 (PubMed:16390871). Interacts with cyclin cig2 (PubMed:8455610, PubMed:11163211). Interacts with cdc37 (PubMed:8455610, PubMed:11163211, PubMed:16390871). Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.