Cyclin-dependent kinase that acts as a master regulator of the mitotic and meiotic cell cycles (By similarity). May drive the G1-S transition (PubMed:7830719). Plays a role in mitotic exit (PubMed:22090345). Plays a role in the expression of morphology-related transcription factors, and especially hyphae-specific genes (PubMed:16710830, PubMed:11809828, PubMed:15659158). Binds distinct cyclin subunits as cells progress through the division cycle or flamentous growth (PubMed:15071502, PubMed:17765684, PubMed:18923418, PubMed:22787279). The CDC28-CLB2 complex regulates cytokinesis partly by phosphorylating the actomyosin ring component IQG1 (PubMed:18923418). The CDC28-CLN3 complex phosphorylates SLA1 which regulates cortical actin patch dynamics (PubMed:22787279). The CDC28-CCN1 complex phosphorylates CDC11 and SEC2 upon induction of filamentous growth (PubMed:17765684). The CDC28-HGC1 complex also phosphorylates SEC2 and maintains CDC11 phosphorylation throughout hyphal growth (PubMed:20639857). Moreover, the CDC28-HGC1 complex phosphorylates and prevents RGA2 from localizing to hyphal tips, leading to localized CDC42 activation for hyphal extension (PubMed:17673907). CDC28-HGC1 phosphorylation of EFG1 represses cell separation genes during hyphal growth (PubMed:19528234). Additional substrates for CDC28 are RFA2 in G1-phase; MOB2, which is required for the maintenance of polarisome components and for inhibition of cell separation in hyphae; and GIN4 to regulate its association to SEP7 and subsequent septin ring assembly (PubMed:23140133, PubMed:22366454, PubMed:21593210). 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-17 or Tyr-18 inactivates the enzyme, while phosphorylation at Thr-166 activates it. Forms several complexes with cyclins CCN1, CLB2, CLN3, and HGC1. The CDC28-CCN1 complex associates with septin CDC11 upon hyphal induction. Interacts with IQG1, RFA2, and HSP90. Expression is increased during exponential growth and repressed by the antifungal drug plagiochin E (PLE). Phosphorylated at Tyr-18 by SWE1 in a cell cycle-dependent manner. Yeast-form and hyphal cells display similar dynamics of phosphorylation and dephosphorylation of Tyr-18. Tyr-18 phosphorylation leads to inhibition of CDC28 kinase activity. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.