BUB3
Description
The BUB3 (BUB3 mitotic checkpoint protein) is a protein-coding gene located on chromosome 10.
BUB3 is a protein involved in the regulation of the Spindle Assembly Checkpoint (SAC). While it 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 biorientation. In directing the kinetochore-microtubule interaction, it ensures the proper (and consequently, bioriented) 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. BUB3 is a crucial component in the formation of the mitotic spindle assembly complex, which forms a complex with other important proteins. For correct segregation of the cells, it is necessary for all mitotic spindles to attach correctly to the kinetochore of each chromosome. This is controlled by the mitotic spindle checkpoint complex which operates as a feedback-response. If there is a signal of a defect in the attachment, mitosis will be stopped to ensure that all chromosomes have an amphitelic binding to spindles. After the error is corrected, the cell will proceed to anaphase.
BUB3 plays a dual role in the spindle assembly checkpoint (SAC) signaling and the establishment of proper kinetochore-microtubule (K-MT) attachments. It promotes the formation of stable end-on bipolar attachments. BUB3 is essential for kinetochore localization of BUB1 and regulates chromosome segregation during oocyte meiosis. The BUB1/BUB3 complex inhibits the anaphase-promoting complex or cyclosome (APC/C) when the SAC is activated. It achieves this by phosphorylating CDC20, the activator of APC/C, which inhibits its ubiquitin ligase activity. This complex can also phosphorylate MAD1L1.
BUB3 is also known as BUB3L, hBUB3.
