Phosphorylation sites in BubR1 that regulate kinetochore attachment, tension, and mitotic exit.
BubR1 kinase is essential for the mitotic checkpoint and also for kinetochores to establish microtubule attachments. In this study, we report that BubR1 is phosphorylated in mitosis on four residues that differ from sites recently reported to be phosphorylated by Plk1 (Elowe, S., S. Hummer, A. Uldschmid, X. Li, and E.A. Nigg. 2007. Genes Dev. 21:2205-2219; Matsumura, S., F. Toyoshima, and E. Nishida. 2007. J. Biol. Chem. 282:15217-15227). S670, the most conserved residue, is phosphorylated at kinetochores at the onset of mitosis and dephosphorylated before anaphase onset. Unlike the Plk1-dependent S676 phosphorylation, S670 phosphorylation is sensitive to microtubule attachments but not to kinetochore tension. Functionally, phosphorylation of S670 is essential for error correction and for kinetochores with end-on attachments to establish tension. Furthermore, in vitro data suggest that the phosphorylation status of BubR1 is important for checkpoint inhibition of the anaphase-promoting complex/cyclosome. Finally, RNA interference experiments show that Mps1 is a major but not the exclusive kinase that specifies BubR1 phosphorylation in vivo. The combined data suggest that BubR1 may be an effector of multiple kinases that are involved in discrete aspects of kinetochore attachments and checkpoint regulation.
Huang
Haomin
H
Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Hittle
James
J
Zappacosta
Francesca
F
Annan
Roland S
RS
Hershko
Avram
A
Yen
Timothy J
TJ
D000705:Anaphase / Q000502:physiology*; D064173:Anaphase-Promoting Complex-Cyclosome; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases; D034741:RNA, Small Interfering; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000378:metabolism*
D018797:Cell Cycle Proteins; D034741:RNA, Small Interfering; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D011505:Protein-Tyrosine Kinases; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human