The processivity of multiubiquitination by the APC determines the order of substrate degradation

Michael Rape, Sashank K. Reddy, Marc W. Kirschner

Research output: Contribution to journalArticlepeer-review

222 Scopus citations


The anaphase-promoting complex (APC) coordinates mitosis and G1 by sequentially promoting the degradation of key cell-cycle regulators. Following the degradation of its substrates in G1, the APC catalyzes the autoubiquitination of its E2 UbcH10. This stabilizes cyclin A and allows it to inactivate APCCdh1. How the APC establishes this complex temporal sequence of ubiquitinations, referred to as substrate ordering, is not understood. Here we show that substrate ordering depends on the relative processivity of substrate multiubiquitination by the APC. Processive substrates obtain ubiquitin chains in a single APC binding event. The multiubiquitination of distributive substrates requires multiple rounds of APC binding, which render it sensitive to lower APC concentrations, competition by processive substrates, and deubiquitination. Consequently, more processive substrates are preferentially multiubiquitinated in vitro and degraded earlier in vivo. The processivity of multiubiquitination is strongly influenced by the D box within the substrate, suggesting that substrate ordering is established by a mechanism intrinsic to APC and its substrates and similar to kinetic proofreading.

Original languageEnglish (US)
Pages (from-to)89-103
Number of pages15
Issue number1
StatePublished - Jan 13 2006
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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