FORMATION OF POLIOMYELITIS SUBVIRAL PARTICLES IN THE YEAST SACCHAROMYCES-CEREVISIAE

The sequence of the poliovirus genome encoding 3CD (a protease) was tr ansferred to the yeast Saccharomyces cerevisiae on expression vectors with either a constitutive or an inducible promoter. Transformants cou ld only be obtained with vectors carrying the inducible transcription unit. Extracts of induced cells were able to cleave cell-free synthesi zed P1, the precursor of the poliovirus capsid proteins, into VP0, VP3 and VP1. In yeast cells constitutively expressing P1, induction of 3C D expression resulted in only trace amounts of processed products. Pro cessing could be improved considerably by simultaneous induction of bo th P1 and 3CD expression. Analysis of extracts of such induced cells r evealed the presence of particles that resembled authentic subviral pa rticles.