The cAMP-PKA signaling initiates mitosis by phosphorylating Bora.

Timely entry into mitosis requires activation of Polo-like kinase 1 (Plk1) by Aurora kinase A (Aurora A), but the upstream signaling trigger remains unclear. Here, we show that cyclic AMP (cAMP) signaling serves as a critical initiator of mitosis in mammalian cells. Specifically, the cAMP-dependent protein kinase (PKA) phosphorylates Bora, enabling it to bind Aurora A and recruit it to the Bora-Plk1 complex during G2 phase, thereby facilitating Aurora A-dependent activation of Plk1. Disruption of PKA-mediated Bora phosphorylation or the Bora-Aurora A interaction impairs Plk1 activation and delays the G2-to-mitosis (G2/M) transition. Conversely, a phospho-mimetic Bora mutant bypasses the requirement for PKA in promoting Bora-Aurora A interaction, Plk1 activation, and mitotic entry. Furthermore, PKA-mediated Bora phosphorylation and the resulting Bora-Aurora A interaction are essential for mitotic entry during DNA damage checkpoint recovery. Together, these findings identify the cAMP-PKA-Bora-Aurora A-Plk1 signaling cascade as a previously unrecognized and critical trigger for mitotic commitment.