Multi-omic analyses reveal a differential contribution of chromatin-associated PP1 holoenzymes to mitotic exit and G1 re-establishment

Mitotic exit is an important part of the cell cycle, requiring the coordination of many chromatin and cytoskeleton remodeling events to successfully complete cell division and maintain cell identity. Protein dephosphorylation is a key step in directing mitotic exit, and protein phosphatase 1 (PP1) is essential to this process; however, the specific contribution of its numerous targeting subunits is still unknown. Here, we have investigated the function of three chromatin-associated PP1-targeting subunits in mitosis exit: Repo-Man, Ki-67, and protein phosphatase 1 nuclear targeting subunit (PNUTS). We generated endogenously tagged, auxin-degradable alleles for each subunit in the human cell line HCT116 and used a multi-omic approach to address their specific contributions toward transcription resumption, chromatin accessibility, and protein dephosphorylation at the transition from mitosis to G1. This approach identified their distinct role in mitotic exit, provided datasets for the cell-cycle community, and highlighted functions for Ki-67 and Repo-Man in genome stability and organization.