CDK1, or Cyclin-dependent kinase 1, is a pivotal protein kinase that plays a critical role in controlling cell cycle progression. CDK1, in complex with cyclins (primarily cyclin B), is crucial for the progression of the cell cycle, particularly for the transition from G2 phase to mitosis (M phase). It helps in the initiation of mitosis by phosphorylating various substrates that are involved in chromosome condensation, nuclear envelope breakdown, and spindle assembly. CDK1 is involved in the regulation of transcription factors and chromatin modifiers, thereby influencing gene expression. It can modulate the activity of transcription factors like RUNX2, SIRT1/2, NPM1, and SREBF1, which mediate cell proliferation and apoptosis by modulating differentiation and metabolic processes. CDK1 plays a complex role in apoptosis. It can inhibit apoptosis through the phosphorylation of caspase-9 and BIRC5 proteins, but it can also promote cell death by phosphorylating and activating Bcl-2 family members. CDK1 regulates mitochondrial dynamics through the phosphorylation of proteins involved in mitochondrial fusion and fission. It also contributes to maintaining cellular redox balance and protects cells from oxidative stress.