Cyclin B1/Cdk1 Coordinates Mitochondrial Respiration for Cell-Cycle G2/M Progression

• A fraction of cyclin B1/Cdk1 proteins localizes to mitochondria at G2/M transition
• A cluster of mitochondrial proteins is phosphorylated by cyclin B1/Cdk1
• Cyclin B1/Cdk1 phosphorylates CI to boost mitochondrial ATP generation
• Cyclin B1/Cdk1 regulates mitochondria metabolism to coordinate G2/M progression

SummaryA substantial amount of mitochondrial energy is required for cell-cycle progression. The mechanisms underlying the coordination of the mitochondrial respiration with cell-cycle progression, especially the G2/M transition, remain to be elucidated. Here, we show that a fraction of cyclin B1/Cdk1 proteins localizes to the matrix of mitochondria and phosphorylates a cluster of mitochondrial proteins, including the complex I (CI) subunits in the respiratory chain. Cyclin B1/Cdk1-mediated CI phosphorylation enhances CI activity, whereas deficiency of such phosphorylation in each of the relevant CI subunits results in impairment of CI function. Mitochondria-targeted cyclin B1/Cdk1 increases mitochondrial respiration with enhanced oxygen consumption and ATP generation, which provides cells with efficient bioenergy for G2/M transition and shortens overall cell-cycle time. Thus, cyclin B1/Cdk1-mediated phosphorylation of mitochondrial substrates allows cells to sense and respond to increased energy demand for G2/M transition and, subsequently, to upregulate mitochondrial respiration for successful cell-cycle progression.

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