A collection of Hfc-mutants (Hfc- High frequency of cytoduction) was obtained using the selective system for cytoduction described previously (1). We investigated the interaction of Hfc-mutations with recesive suppressors sup35, sup45 and cytoplasmic suppressor psi - prionic form of Sup35 protein. Suppression efficiency of ade1-14 (UGA) and of his7-1 (UAA) by psi, sup35 or sup45 was studied in tetrad analysis of hybrids homozygous for the nonsense alleles and heterozygous for Hfc and each of suppressors. One Hfc-mutant neutralized the suppression by both sup35 and sup45 completely.The same effect was shown toward psi without cureing of it. Four mutants only partialy lowered the suppression effect of both sup35 and sup45 and one mutant had antisuppressor effect only toward sup45. Mutants with defect in karyogamy and increased translation fidelity simultaneously (HfcAsu-mutants) suggest connection between translation termination and cell processes in yeast. Nothern blot hybridisation had not revealed any change in the ratio of two transcripts of SUP35 gene in HfcAsu mutants compared with original strain. (1)Karpova T.S. and Inge-Vechtomov S.G./Genetica.1984.v20.p398.(in russian)