PROHIBITIN, A PUTATIVE NEGATIVE CONTROL ELEMENT PRESENT IN PNEUMOCYSTIS-CARINII

Little is known about the molecules involved in the regulation of Pneu mocystis carinii replication and development in vitro and in vivo. We describe in this report the identification of a P. carinii gene encodi ng the P. carinii prohibitin protein. In mammals, the prohibitin gene product has been shown to negatively regulate cell proliferation. A cD NA clone encoding the P. carinii prohibitin gene was isolated from a P . carinii cDNA library and identified on the basis of amino acid seque nce homology with prohibitin from mammalian sources, Southern blot ana lysis confirmed that the prohibitin cDNA clone was of P. carinii origi n. Western blot analysis of total P. carinii protein indicated that th e prohibitin gene is transcribed and translated in vivo. The P. carini i prohibitin gene was expressed in vivo in human fibroblasts and shown to arrest the cell cycle in the G(1) phase. The results obtained sugg est a potential role for P. carinii prohibitin in the regulation of P. carinii proliferation and development.