MOS AND THE CELL-CYCLE - THE MOLECULAR-BASIS OF THE TRANSFORMED PHENOTYPE

The product of the mos proto-oncogene is a serine/threonine kinase that is expressed at high levels in germ cells. Mos is a regulator of meiotic maturation, and is required for the initiation and progression of oocyte meiotic maturation that leads to the production of unfertilized eggs. Mos is also a component of cytostatic factor, an activity that is believed to arrest oocyte maturation at meiotic metaphase II. There is evidence showing that the Mos protein is associated with tubulin in unfertilized eggs and transformed cells, raising the possibility that it is involved in the microtubular reorganization that occurs during M-phase. Inappropriate expression of its M-phase activity during interphase of the cell cycle may be responsible for its transforming activity.