M-phase promoting factors from eggs of Xenopus laevis.
When an M-phase promoting factor (MPF) is injected into Xenopus oocytes, which are naturally arrested at the G2/prophase boundary, it induces rapid entry of the cells into M-phase. MPF is present in late G2 and in M-phase of a variety of cell types, such as Xenopus eggs (naturally arrested in M), cleaving embryos, yeast, HeLa, and CHO cultures. MPF has been purified approximately 50-fold from eggs. It is stabilized by gamma-thio-ATP and by phosphoprotein phosphatase inhibitors. It runs as a protein of approximately 100 kd size on gel filtration. Oocytes contain a precursor of MPF, which is activated by post-translational means when a small amount of purified MPF is injected into the cell. Thus, MPF appears to be an auto-activating cytoplasmic trigger of M-phase. At anaphase of the cell cycle, MPF is inactivated due to the appearance of an 'anti-MPF' activity. Monoclonal antibodies have been prepared to partially purified MPF stabilized by gamma-thio-ATP, and several preparations which inactivate MPF were obtained. The antibodies are directed against thio-phosphate groups carried by a set of proteins including MPF. This indicates that MPF is present in our active preparations as a thio-phosphoprotein. These and other data suggest that MPF is normally activated in the cell cycle by a phosphorylation reaction.
D000818:Animals; D000911:Antibodies, Monoclonal; D002453:Cell Cycle; D006133:Growth Substances / Q000096:biosynthesis / Q000302:isolation & purification; D016200:Maturation-Promoting Factor; D008938:Mitosis / Q000187:drug effects; D009865:Oocytes / Q000166:cytology / Q000378:metabolism*; D013997:Time Factors; D014982:Xenopus laevis
D000911:Antibodies, Monoclonal; D006133:Growth Substances; D016200:Maturation-Promoting Factor