Apc4 is one of the larger of the subunits of the anaphase-promoting complex or cyclosome. This family represents the long domain downstream of the WD40 repeat/s that are present on the Apc4 subunits. The anaphase-promoting complex is a multiprotein subunit E3 ubiquitin ligase complex that controls segregation of chromosomes and exit from mitosis in eukaryotes [1,2]. Results in C.elegans show that the primary essential role of the spindle assembly checkpoint is not in the chromosome segregation process itself but rather in delaying anaphase onset until all chromosomes are properly attached to the spindle. the APC/C is likely to be required for all metaphase-to-anaphase transitions in a multicellular organism [3].

1: The anaphase-promoting complex: proteolysis in mitosis and beyond. Peters JM; Mol Cell. 2002;9:931-943. PMID:12049731

2: The anaphase promoting complex/cyclosome: a machine designed to destroy. Peters JM; Nat Rev Mol Cell Biol. 2006;7:644-656. PMID:16896351

3: EMB-30: an APC4 homologue required for metaphase-to-anaphase transitions during meiosis and mitosis in Caenorhabditis elegans. Furuta T, Tuck S, Kirchner J, Koch B, Auty R, Kitagawa R, Rose AM, Greenstein D; Mol Biol Cell. 2000;11:1401-1419. PMID:10749938