ARE PROTEASOMES INVOLVED IN THE FORMATION OF THE KINETOCHORE

Proteasomes catalyse the degradation of proteins responsible for the r egulation of mitosis enabling the cell to complete cell division. We h ave studied the effect of an inhibitor of the chymotrypsin-like activi ty of the proteasome on the trilaminar structure of the kinetochore in HeLa cells. Whereas a role for the proteasome in the degeneration of the kinetochore was predicted, we found instead that the inhibitor str ongly retarded kinetochore development. We observed different 'develop mental' stages of the kinetochore from the fibrous ball of a 'prekinet ochore' to the 'mature' kinetochore in one cell. The data presented he re support the proposition that proteasomes are involved in kinetochor e formation.