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Mol Cell. 2016 Aug 18;63(4):593-607. doi: 10.1016/j.molcel.2016.07.003. Epub 2016 Aug 10.

Cryo-EM of Mitotic Checkpoint Complex-Bound APC/C Reveals Reciprocal and Conformational Regulation of Ubiquitin Ligation.

Author information

1
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
2
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA.
3
Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria.
4
Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany.
5
Donnelly Centre for Cellular and Biomolecular Research and Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5S3E1, Canada.
6
Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), 1030 Vienna, Austria. Electronic address: jan-michael.peters@imp.ac.at.
7
Max Planck Institute for Biophysical Chemistry, 37077 Göttingen, Germany. Electronic address: hstark1@gwdg.de.
8
Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN 38105, USA; Howard Hughes Medical Institute, St. Jude Children's Research Hospital, Memphis, TN 38105, USA. Electronic address: brenda.schulman@stjude.org.

Abstract

The mitotic checkpoint complex (MCC) coordinates proper chromosome biorientation on the spindle with ubiquitination activities of CDC20-activated anaphase-promoting complex/cyclosome (APC/C(CDC20)). APC/C(CDC20) and two E2s, UBE2C and UBE2S, catalyze ubiquitination through distinct architectures for linking ubiquitin (UB) to substrates and elongating polyUB chains, respectively. MCC, which contains a second molecule of CDC20, blocks APC/C(CDC20)-UBE2C-dependent ubiquitination of Securin and Cyclins, while differentially determining or inhibiting CDC20 ubiquitination to regulate spindle surveillance, checkpoint activation, and checkpoint termination. Here electron microscopy reveals conformational variation of APC/C(CDC20)-MCC underlying this multifaceted regulation. MCC binds APC/C-bound CDC20 to inhibit substrate access. However, rotation about the CDC20-MCC assembly and conformational variability of APC/C modulate UBE2C-catalyzed ubiquitination of MCC's CDC20 molecule. Access of UBE2C is limiting for subsequent polyubiquitination by UBE2S. We propose that conformational dynamics of APC/C(CDC20)-MCC modulate E2 activation and determine distinctive ubiquitination activities as part of a response mechanism ensuring accurate sister chromatid segregation.

PMID:
27522463
PMCID:
PMC5148128
DOI:
10.1016/j.molcel.2016.07.003
[Indexed for MEDLINE]
Free PMC Article

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