Cdk1 phosphorylation of fission yeast paxillin inhibits its cytokinetic ring localization

Abstract

Divisions of the genetic material and cytoplasm are coordinated spatially and temporally to ensure genome integrity. This coordination is mediated in part by the major cell cycle regulator cyclin-dependent kinase (Cdk1). Cdk1 activity peaks during mitosis, but during mitotic exit/cytokinesis Cdk1 activity is reduced, and phosphorylation of its substrates is reversed by various phosphatases including Cdc14, PP1, PP2A and PP2B. Cdk1 is known to phosphorylate several components of the actin- and myosin-based cytokinetic ring (CR) that mediates division of yeast and animal cells. Here we show that Cdk1 also phosphorylates the Schizosaccharomyces pombe CR-component paxillin Pxl1. We determined that both the Cdc14 phosphatase Clp1 and the PP1 phosphatase Dis2 contribute to Pxl1 dephosphorylation at mitotic exit, but PP2B/calcineurin does not. Preventing Pxl1 phosphorylation by Cdk1 results in increased Pxl1 levels, precocious Pxl1 recruitment to the division site, and increases the duration of CR constriction. In vitro, Cdk1-mediated phosphorylation of Pxl1 inhibits its interaction with the F-BAR domain of the cytokinetic scaffold Cdc15, thereby disrupting a major mechanism of Pxl1 recruitment. Thus, Pxl1 is a novel substrate through which S. pombe Cdk1 and opposing phosphatases coordinate mitosis and cytokinesis.

Lipid Polarization during Cytokinesis

“…The F-BAR domain protein CDC15 plays important roles in the assembly of the contractile ring in the fission yeast Schizosaccharomyces pombe [ 54 ]. CDC15-mediated contractile ring assembly involves a sequence of events including dephosphorylation of the hyperphosphorylated state at interphase, binding to formin CDC12, localization to the site of cytokinesis, recruitment of Myo1 (class II myosin heavy chain), and activation of the Arp2/3 complex to promote actin cable network formation [ 53 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 ].…”