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Molecular and Cellular Biology, August 2001, p. 5190-5199, Vol. 21, No. 15
Department of Oncology, DNAX Research
Institute, Palo Alto, California 94304-1104
Received 8 December 2000/Returned for modification 29 January
2001/Accepted 24 April 2001
Activation of the anaphase-promoting complex (APC) is required for
anaphase initiation and for exit from mitosis in mammalian cells.
Cdc20, which specifically recognizes APC substrates involved in the
metaphase-to-anaphase transition, plays a pivotal role in APC
activation through direct interaction with the APC. The activation of
the APC by Cdc20 is prevented by the interaction of Cdc20 with Mad2
when the spindle checkpoint is activated. Using deletion mutagenesis
and peptide mapping, we have identified the sequences in Cdc20 that
target it to Mad2 and the APC, respectively. These sequences are
distinct but overlapping, providing a possible structural explanation
for the internal modulation of the APC-Cdc20 complex by Mad2. In the
course of these studies, a truncation mutant of Cdc20 (1-153) that
constitutively binds Mad2 but fails to bind the APC was identified.
Overexpression of this mutant induces the formation of multinucleated
cells and increases their susceptibility to undergoing apoptosis when
treated with microtubule-inhibiting drugs. Our experiments demonstrate
that disruption of the Mad2-Cdc20 interaction perturbs the mitotic
checkpoint, leading to premature activation of the APC, sensitizing the
cells to the cytotoxic effects of microtubule-inhibiting drugs.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.15.5190-5199.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification of an Overlapping Binding Domain on
Cdc20 for Mad2 and Anaphase-Promoting Complex: Model for Spindle
Checkpoint Regulation
*
Corresponding author. Mailing address: DNAX Research
Institute, 901 California Ave., Palo Alto, CA 94304. Phone: (650)
496-1257. Fax: (650) 496-1200. E-mail:
emma.lees{at}dnax.org.
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