MAD2L1BP (MAD2L1 binding protein), also known as CMT2, is a 274 amino acid protein that localizes to the nucleoplasm during early mitosis and to the spindle from metaphase through anaphase. Functioning as a component of the spindle checkpoint (which delays the onset of anaphase until kineotochore attachment is complete), MAD2L1BP is thought to coordinate cell cycle events in late mitosis, possibly binding to MAD2, thereby silencing the spindle checkpoint and allowing mitosis to proceed. MAD2L1BP is expressed as multiple alternative spliced isforms that, upon DNA damage, may be phosphorylated by ATM or ATR. The gene encoding MAD2L1BP maps to human chromosome 6, which contains 170 million base pairs and comprises nearly 6% of the human genome.