Failure of kinetochore development and mitotic spindle formation in okadaic acid-induced premature mitosis in HeLa cells.

The mitotic events associated with okadaic acid (OA)-induced premature chromosome condensation (PCC) in S-phase-blocked HeLa cells were studied at the light microscope, immunofluorescence, and electron microscope level. The development of PCC in these cells has been compared with that in multinucleate cells and also in uninucleate hamster cells induced by caffeine. In OA-induced PCC, the nuclear envelope breaks down and chromosomes condense, but the mitotic spindle and trilaminar kinetochores fail to develop. In S-phase PCC in multinucleate cells, only the mitotic spindle does not develop, whereas in caffeine-induced PCC, all these events are found to be associated. The possible difference in their pathways of induction and, in this connection, the dissociability of the early mitotic events have been discussed.