APC1 (anaphase-promoting complex subunit 1) is a meiotic checkpoint regulator that is a member of the E3 enzyme family. This protein contains Rpn1/2repeats and has a molecular weight of approximately 216 kD. The APC1 protein is located in the nucleus during interphase, and at the centrosome during metaphase/anaphase. This protein comprises one subunit of the anaphase promoting complex including APC1-8, and other probable complex proteins APC9-11, Cdc26, Mnd2, Swm1. The APC1 protein functions as a probable scaffold for complex assembly, a multisubunit cell cycle ubiquitin ligase, and a regulator of sister chromatid separation by degrading securins. In addition, this protein functions in ubiquitin-dependent cyclin catabolism, metaphase/anaphase transition, and spindle elongation. The APC complex is inactivated by protein kinase A and is activated by CDC20 and Cdh1. The APC1 protein is phosphorylated by Cdk1-cyclin B and can also be ubiquitinated and targeted for degradation. The Poly6017 antibody has been shown to be useful for Western blotting of the human APC1 protein.