Aurora A regulates the activity of HURP by controlling the accessibility of its microtubule-binding domain.
HURP is a spindle-associated protein that mediates Ran-GTP-dependent assembly of the bipolar spindle and promotes chromosome congression and interkinetochore tension during mitosis. We report here a biochemical mechanism of HURP regulation by Aurora A, a key mitotic kinase that controls the assembly and function of the spindle. We found that HURP binds to microtubules through its N-terminal domain that hyperstabilizes spindle microtubules. Ectopic expression of this domain generates defects in spindle morphology and function that reduce the level of tension across sister kinetochores and activate the spindle checkpoint. Interestingly, the microtubule binding activity of this N-terminal domain is regulated by the C-terminal region of HURP: in its hypophosphorylated state, C-terminal HURP associates with the microtubule-binding domain, abrogating its affinity for microtubules. However, when the C-terminal domain is phosphorylated by Aurora A, it no longer binds to N-terminal HURP, thereby releasing the inhibition on its microtubule binding and stabilizing activity. In fact, ectopic expression of this C-terminal domain depletes endogenous HURP from the mitotic spindle in HeLa cells in trans, suggesting the physiological importance for this mode of regulation. We concluded that phosphorylation of HURP by Aurora A provides a regulatory mechanism for the control of spindle assembly and function.
Wong
Jim
J
Department of Biological Sciences, Stanford University, Stanford, CA 94305-5020, USA.
Lerrigo
Robert
R
Jang
Chang-Young
CY
Fang
Guowei
G
D000595:Amino Acid Sequence; D064127:Aurora Kinases; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000201:enzymology; D008870:Microtubules / Q000201:enzymology* / Q000378:metabolism; D008938:Mitosis; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000378:metabolism; D008941:Spindle Apparatus / Q000201:enzymology; D014404:Tubulin / Q000378:metabolism
C465041:DLGAP5 protein, human; D009363:Neoplasm Proteins; D021122:Protein Subunits; D014404:Tubulin; D064127:Aurora Kinases; D017346:Protein Serine-Threonine Kinases