The SUP35 omnipotent suppressor gene is involved in the maintenance of the non-Mendelian determinant psi+ in the yeast Saccharomyces cerevisiae.

The SUP35 gene of yeast Saccharomyces cerevisiae encodes a 76.5-kD ribosome-associated protein (Sup35p), the C-terminal part of which exhibits 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 present study the SUP35 wild-type gene was replaced with deletion alleles generated in vitro that encode Sup35p lacking all or a part of the unique N-terminal region. These 5'-deletion alleles lead, in a haploid strain, 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 trait. A set of the plasmid-borne deletion alleles of the SUP35 gene was tested for the ability to maintain psi+. It was shown that the first 114 amino acids of Sup35p are sufficient to maintain the psi+ determinant. We propose that the Sup35p serves as a trans-acting factor required for the maintenance of psi+.