title: The RZZ complex requires the N-terminus of KNL1 to mediate optimal Mad1 kinetochore localization in human cells.
abstract: The spindle assembly checkpoint is a surveillance mechanism that blocks anaphase onset until all chromosomes are properly attached to microtubules of the mitotic spindle. Checkpoint activity requires kinetochore localization of Mad1/Mad2 to inhibit activation of the anaphase promoting complex/cyclosome in the presence of unattached kinetochores. In budding yeast and Caenorhabditis elegans, Bub1, recruited to kinetochores through KNL1, recruits Mad1/Mad2 by direct linkage with Mad1. However, in human cells it is not yet established which kinetochore protein(s) function as the Mad1/Mad2 receptor. Both Bub1 and the RZZ complex have been implicated in Mad1/Mad2 kinetochore recruitment; however, their specific roles remain unclear. Here, we investigate the contributions of Bub1, RZZ and KNL1 to Mad1/Mad2 kinetochore recruitment. We find that the RZZ complex localizes to the N-terminus of KNL1, downstream of Bub1, to mediate robust Mad1/Mad2 kinetochore localization. Our data also point to the existence of a KNL1-, Bub1-independent mechanism for RZZ and Mad1/Mad2 kinetochore recruitment. Based on our results, we propose that in humans, the primary mediator for Mad1/Mad2 kinetochore localization is the RZZ complex.
authors.affiliation: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Gina V
authors.initials: GV
authors.lastname: Caldas
authors.affiliation: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Tina R
authors.initials: TR
authors.lastname: Lynch
authors.affiliation: Natural Resource Ecology Laboratory, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Ryan
authors.initials: R
authors.lastname: Anderson
authors.affiliation: Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
authors.forename: Sana
authors.initials: S
authors.lastname: Afreen
authors.affiliation: Department of Cell and Molecular Biology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA dileep.varma@northwestern.edu.
authors.forename: Dileep
authors.initials: D
authors.lastname: Varma
authors.affiliation: Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA jdeluca@colostate.edu.
authors.forename: Jennifer G
authors.initials: JG
authors.lastname: DeLuca
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D064246:Mad2 Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D018797:Cell Cycle Proteins; C472643:Knl1 protein, human; C501384:MAD1L1 protein, human; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases
keywords: Bub1; KNL1; Mad1; RZZ complex; kinetochore; spindle checkpoint