Post-translational modifications of various polypeptides in relation to the first mitosis in BALB/c mouse ova

After X-irradiation at pronuclear stage, mice eggs from certain strains are reversibly blocked in G2 phase of the first cell cycle. However, evolution of polypeptide synthesis takes place in a normal way, except for three polypeptides sets of 30, 35 and 45 kd molecular weight that appear in dividing controls and not in blocked, irradiated eggs. It is shown that those first mitosis-specific polypeptides result from post-translational modifications, involving phosphorylations.