The Sup35 Omnipotent Suppressor Gene Is Involved in the Maintenance of the Non-Mendelian Determinant [Psi(+)] in the Yeast Saccharomyces Cerevisiae

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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-1α 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(+)].

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