The HECT E3 ligase Smurf2 is required for Mad2-dependent spindle assembly checkpoint.
Activation of the anaphase-promoting complex/cyclosome (APC/C) by Cdc20 is critical for the metaphase-anaphase transition. APC/C-Cdc20 is required for polyubiquitination and degradation of securin and cyclin B at anaphase onset. The spindle assembly checkpoint delays APC/C-Cdc20 activation until all kinetochores attach to mitotic spindles. In this study, we demonstrate that a HECT (homologous to the E6-AP carboxyl terminus) ubiquitin ligase, Smurf2, is required for the spindle checkpoint. Smurf2 localizes to the centrosome, mitotic midbody, and centromeres. Smurf2 depletion or the expression of a catalytically inactive Smurf2 results in misaligned and lagging chromosomes, premature anaphase onset, and defective cytokinesis. Smurf2 inactivation prevents nocodazole-treated cells from accumulating cyclin B and securin and prometaphase arrest. The silencing of Cdc20 in Smurf2-depleted cells restores mitotic accumulation of cyclin B and securin. Smurf2 depletion results in enhanced polyubiquitination and degradation of Mad2, a critical checkpoint effector. Mad2 is mislocalized in Smurf2-depleted cells, suggesting that Smurf2 regulates the localization and stability of Mad2. These data indicate that Smurf2 is a novel mitotic regulator.
Osmundson
Evan C
EC
Department of Molecular Pharmacology and Biological Chemistry, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA.
Ray
Dipankar
D
Moore
Finola E
FE
Gao
Qingshen
Q
Thomsen
Gerald H
GH
Kiyokawa
Hiroaki
H
D000705:Anaphase; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002384:Catalysis; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D018385:Centrosome / Q000201:enzymology; D045584:Chromosome Positioning; D020090:Chromosome Segregation; D048749:Cytokinesis; D004789:Enzyme Activation; D020868:Gene Silencing; D006801:Humans; D064246:Mad2 Proteins; D008677:Metaphase; D008954:Models, Biological; D021381:Protein Transport; D012097:Repressor Proteins / Q000378:metabolism*; D008941:Spindle Apparatus / Q000201:enzymology*; D013816:Thermodynamics; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*
D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; C577697:MAD2L1 protein, human; D064246:Mad2 Proteins; D012097:Repressor Proteins; C471641:SMURF2 protein, human; D044767:Ubiquitin-Protein Ligases