Budding Uninhibited By Benzimidazoles 3 (BUB3)

Bub3 is a protein involved with the regulation of the Spindle Assembly Checkpoint (SAC); though BUB3 is non-essential in yeast, it is essential in higher eukaryotes. As one of the checkpoint proteins, Bub3 delays the irreversible onset of anaphase through direction of kinetochore localization during prometaphase to achieve biorentation. In directing the kinetochore-microtubule interaction, this ensures the proper attachment of the chromosomes prior to anaphase.

Bub3 and its related proteins that form the Spindle Assembly Checkpoint (SAC) inhibit the action of the Anaphase Promoting Complex (APC), preventing early anaphase entry and mitotic exit; this serves as a mechanism for the fidelity of chromosomal segregation