Mitotic Protein Kinase 1: Role in Spindle Assembly Checkpoint Revisited

Cell division is a highly regulated process and involves sequential activation and deactivation of a number of proteins. Mitotic protein kinase (MPS1) is a part of the spindle assembly checkpoint (SAC) activated during prometaphase and metaphase that prevents chromosome misalignment by arresting the cell in mid-mitosis until all of the chromosomes is properly attached to the mitotic spindle [1]. Multiple cancers show alterations of the SAC machinery leading to chromosome missegregation and aneuploidy. MPS1 functions as a dual-specificity kinase that is critical for the recruitment of SAC proteins to unattached kinetochores, proper mitotic progression, and centrosome duplication [2]. Overexpression of Mps1 is observed in a number of cancer cell lines and tumor types, including breast cancer, gastric, colorectal cancer, anaplastic thyroid carcinoma, lung cancers and gliomas, also correlating with high histological grade and tumor aggressiveness [3,4]. High levels of Mps1 contribute to tumorigenesis by attenuating the spindle assembly checkpoint [5].