THE SUP35 OMNIPOTENT SUPPRESSOR GENE IS INVOLVED IN THE MAINTENANCE OF THE NON-MENDELIAN DETERMINANT [PSI(-CEREVISIAE()] IN THE YEAST SACCHAROMYCES)

The SUP35 gene of yeast Saccharomyces cerevisiae encodes a 76.5-kD rib osome-associated protein (Sup35p), the G-terminal part of which exhibi ts a high degree of similarity to EF-1 alpha elongation factor, while its N-terminal region is unique. Mutations in or overexpression of the SUP35 gene can generate an omnipotent suppressor effect. In the prese nt study the SUP35 wild-type gene was replaced with deletion alleles g enerated in vitro that encode Sup35p lacking all or a part of the uniq ue N-terminal region. These 5'-deletion alleles lead, in a haploid str ain, simultaneously to an antisuppressor effect and to loss of the non -Mendelian determinant [psi(+)]. The antisuppressor effect is dominant while the elimination of the [psi(+)] determinant is a recessive trai t. A set of the plasmid-borne deletion alleles of the SUP35 gene was t ested for the ability to maintain [psi(+)]. It was shown that the firs t 114 amino acids of Sup35p are sufficient to maintain the [psi(+)] de terminant. We propose that the Sup35p serves as a trans-acting factor required for the maintenance of [psi(+)].