title: Substrate-specific activation of the mitotic kinase Bub1 through intramolecular autophosphorylation and kinetochore targeting.
abstract: During mitosis of human cells, the kinase Bub1 orchestrates chromosome segregation through phosphorylating histone H2A and the anaphase-promoting complex/cyclosome activator Cdc20. Bub1-mediated H2A-T120 phosphorylation (H2A-pT120) at kinetochores promotes centromeric sister-chromatid cohesion, whereas Cdc20 phosphorylation by Bub1 contributes to spindle checkpoint signaling. Here, we show that phosphorylation at the P+1 substrate-binding loop of human Bub1 enhances its activity toward H2A but has no effect on its activity toward Cdc20. We determine the crystal structure of phosphorylated Bub1. A comparison between structures of phosphorylated and unphosphorylated Bub1 reveals phosphorylation-triggered reorganization of the P+1 loop. This activating phosphorylation of Bub1 is constitutive during the cell cycle. Enrichment of H2A-pT120 at mitotic kinetochores requires kinetochore targeting of Bub1. The P+1 loop phosphorylation of Bub1 appears to occur through intramolecular autophosphorylation. Our study provides structural and functional insights into substrate-specific regulation of a key mitotic kinase and expands the repertoire of kinase activation mechanisms.
authors.affiliation: Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
authors.forename: Zhonghui
authors.initials: Z
authors.lastname: Lin
authors.affiliation: Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
authors.forename: Luying
authors.initials: L
authors.lastname: Jia
authors.affiliation: Department of Biophysics, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
authors.forename: Diana R
authors.initials: DR
authors.lastname: Tomchick
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA.
authors.forename: Xuelian
authors.initials: X
authors.lastname: Luo
authors.affiliation: Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA; Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Road, Dallas, TX 75390, USA. Electronic address: hongtao.yu@utsouthwestern.edu.
authors.forename: Hongtao
authors.initials: H
authors.lastname: Yu
mesh_terms: D020134:Catalytic Domain; D064199:Cdc20 Proteins / Q000378:metabolism*; D002453:Cell Cycle; D018360:Crystallography, X-Ray; D006367:HeLa Cells; D006657:Histones / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D012694:Serine / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D064199:Cdc20 Proteins; D006657:Histones; C577488:CDC20 protein, human; D012694:Serine; C584277:BUB1 protein, human; D017346:Protein Serine-Threonine Kinases