title: Substrate degradation by the anaphase promoting complex occurs during mitotic slippage.
abstract: Microtubule targeting drugs are successful in chemotherapy because they indefinitely activate the spindle assembly checkpoint. The spindle assembly checkpoint monitors proper attachment of all kinetochores to microtubules and tension between the kinetochores of sister chromatids to prevent premature anaphase entry. To this end, the activated spindle assembly checkpoint suppresses the E3 ubiquitin ligase activity of the anaphase-promoting complex (APC). In the continued presence of conditions that activate the spindle assembly checkpoint, cells eventually escape from mitosis by "slippage". It has not been directly tested whether APC activation accompanies slippage. Using cells blocked in mitosis with the microtubule assembly inhibitor nocodazole, we show that mitotic APC substrates are degraded upon mitotic slippage. To confirm that APC is normally activated upon mitotic slippage we have found that knockdown of Cdc20 and Cdh1, two mitotic activators of APC, prevents the degradation of APC substrates during mitotic slippage. We provide the first direct demonstration that despite conditions that activate the spindle checkpoint, APC is indeed activated upon mitotic slippage of cells to interphase cells. Activation of the spindle checkpoint by microtubule targeting drugs used in chemotherapy may not indefinitely prevent APC activation.
authors.affiliation: Sidney Kimmel Cancer Center, San Diego, CA, USA.
authors.forename: Jinho
authors.initials: J
authors.lastname: Lee
authors.forename: Jin Ah
authors.initials: JA
authors.lastname: Kim
authors.forename: Robert L
authors.initials: RL
authors.lastname: Margolis
authors.forename: Rati
authors.initials: R
authors.lastname: Fotedar
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome; D015703:Antigens, CD; D000970:Antineoplastic Agents / Q000494:pharmacology; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D016193:G1 Phase; D055785:Gene Knockdown Techniques; D045325:HCT116 Cells; D006801:Humans; D008938:Mitosis; D015739:Nocodazole / Q000494:pharmacology; D016196:S Phase; D008941:Spindle Apparatus / Q000378:metabolism; D013379:Substrate Specificity; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000970:Antineoplastic Agents; C513384:CDH1 protein, human; D015820:Cadherins; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C577488:CDC20 protein, human; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases; D015739:Nocodazole