The processivity of multiubiquitination by the APC determines the order of substrate degradation.
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 APC(Cdh1). 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.
Rape
Michael
M
Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
Reddy
Sashank K
SK
Kirschner
Marc W
MW
D064173:Anaphase-Promoting Complex-Cyclosome; D001345:Autoradiography; D015153:Blotting, Western; D015820:Cadherins / Q000378:metabolism; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002478:Cells, Cultured; D019925:Cyclin A / Q000378:metabolism; D064248:Geminin; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008938:Mitosis; D013997:Time Factors; D044763:Ubiquitin-Conjugating Enzymes / Q000378:metabolism; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism*
D015820:Cadherins; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D019925:Cyclin A; C577995:GMNN protein, human; D064248:Geminin; D014452:Ubiquitins; C577488:CDC20 protein, human; C105156:UBE2C protein, human; D044763:Ubiquitin-Conjugating Enzymes; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome