MITOSIS-PROMOTING FACTOR-MEDIATED SUPPRESSION OF A CLONED DELAYED RECTIFIER POTASSIUM CHANNEL EXPRESSED IN XENOPUS OOCYTES

The cell cycle is the crucial process that leads to mitosis in all cel l types. The dramatic redirectioning of many cellular processes during the cycle is known to involve ion channels, either changing their lev el of expression or their voltage dependence, as in the case of inward rectifiers. Here we describe the specific inhibition of heterologousl y expressed ionic channels at the onset of maturation in Xenopus oocyt es. In cells expressing rat eag (R-eag) potassium channels, maturation induces a dramatic reduction in the current amplitude, which is almos t complete in most cases. The key molecule in oocyte maturation, the m itosis-promoting factor (a complex of cyclin B and p34(cdc2)), is able to induce similar changes when injected into the oocytes.