title: Centralspindlin assembly and 2 phosphorylations on MgcRacGAP by Polo-like kinase 1 initiate Ect2 binding in early cytokinesis.
abstract: Cytokinesis is the final step of cell division which partitions genetic and cytosolic content into daughter cells. Failed cytokinesis causes polyploidy, genetic instability, and cancer. Kinases use phosphorylation to regulate the timing and location of the cytokinetic furrow. Polo-like kinase 1 (Plk1) is an essential mitotic kinase that triggers cytokinesis by phosphorylating MgcRacGAP to create a docking site for Ect2 at the central spindle. Ect2 binds to MgcRacGAP via its N-terminal BRCT domain (BRCA1 C-terminal), which docks at specific phosphorylated residues. Here we investigate the minimal Plk1-dependent phosphorylation sites required for cytokinesis onset. We demonstrate that phosphorylation of the major MgcRacGAP site, S157, is necessary but not sufficient to bind the Ect2 BRCT domain. Phosphorylation of an additional residue on MgcRacGAP at S164 is also required to elicit efficient binding. Surprisingly, BRCT binding additionally requires MKLP1 and its cognate interacting N-terminal domain of MgcRacGAP. Our findings indicate that central spindle assembly and 2 Plk1-dependent phosphorylations are required to establish efficient binding of the Ect2 BRCT in early cytokinesis. We propose that these requirements establish a high threshold to restrain premature or ectopic cytokinesis.
authors.affiliation: a Hematology/Oncology Division ; Department of Medicine ; University of Wisconsin Carbone Cancer Center ; Madison , WI USA.
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Kim
authors.forename: Feng
authors.initials: F
authors.lastname: Guo
authors.forename: Sarang
authors.initials: S
authors.lastname: Brahma
authors.forename: Yongna
authors.initials: Y
authors.lastname: Xing
authors.forename: Mark E
authors.initials: ME
authors.lastname: Burkard
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism*; D048749:Cytokinesis; D020690:GTPase-Activating Proteins / Q000737:chemistry / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D016547:Kinesins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000378:metabolism; D000097869:Polo-Like Kinase 1
chemical_list: D018797:Cell Cycle Proteins; D020690:GTPase-Activating Proteins; D016547:Kinesins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D020742:rhoA GTP-Binding Protein; D000097869:Polo-Like Kinase 1; C489850:ECT2 protein, human; C115995:mgcRacGAP
keywords: BRCT, BRCA1 C-terminal; Cyk4; Ect2; Ect2, Epithelial cell transforming sequence 2; MKLP1; MKLP1, Mitotic kinesin-like protein 1; MgcRacGAP, Male germ cell RacGAP; Plk1; Plk1, Polo-like kinase 1.; RACGAP1