MOB1 was first identified in yeast as a protein that binds to Mps with essential roles in the completion of mitosis and the maintenance of ploidy. Its Drosophila and mammalian homologs, Mats and MOB1, respectively, are involved in the Hippo signaling tumor suppressor pathway, which plays a critical role in organ size regulation and which has been implicated in cancer development . There are two MOB1 proteins in humans, MOB1α and MOB1β, that are encoded by two different genes but which have greater than 95% amino acid sequence identity.