Description
The human Mps1/TTK kinase was originally identified in a screen for novel tyrosine kinases by using a phosphotyrosine antibody to screen a T-cell cDNA expression library. Using a similar strategy, the mouse homologue, esk, was also cloned from an embryonal carcinoma cell line. It was determined subsequently that esk was the mouse orthologue of yeast MPS1. Human Mps1 is detectable in all proliferating human cells and tissues.Expression of the human Mps1 gene is markedly reduced or absent in resting cells and in tissues with a low proliferative index. Levels of human Mps1 mRNA and protein are very low in starved cells. When cells are induced to enter the cell cycle, levels of human Mps1 mRNA, protein and kinase activity increase at the G1/S phase of the cell cycle and peak in G2/M.Human Mps1 mRNA levels, as well as kinase activity, drop sharply in early G1, whereas protein levels are largely maintained. Human Mps1 may play a role in cell cycle control