MAD2

MAD2 (mitotic arrest deficient 2) is one of the kinetochore proteins present on the chromosomes during cell division. It is involved in making sure all chromosomes are attached to the mitotic spindle before the beginning of anaphase.

During mitosis (and meiosis), the attachment of sister chromatids is monitored by the spindle checkpoint. If the sister chromatids do not attach to opposite poles, the spindle checkpoint is triggered. Mad2, which is normally bound to Mad1 in a Mad1/Mad2 complex then binds to the anaphase-promoting complex (APC) to form an APC/Mad2 complex. Binding to the APC prevents the formation of the APC/Cdc20p complex which is necessary to begin anaphase. The binding of Mad2 proteins to the APC effectively prevents the cell from transitioning into the anaphase until all of the chromatids are properly attached to opposite spindle pole bodies.