Recessive Lethal Amber Suppressors in Yeast

Brandriss, M C; Soll, Larry; Botstein, David

doi:10.1093/genetics/79.4.551

Cited by 33 publications

(3 citation statements)

References 17 publications

(11 reference statements)

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“…It now appears that over suppression may likewise be found to cause some amber suppressors to be recessive lethals. However, the recessive-lethal amber suppressor described by HAWTHORNE and LEU-POLD (1974) and BRANDRISS, SOLL and BOTSTEIN (1975) was suggested to result from the loss of an essential tRNA gene and not from over suppression.…”

Section: Discussionmentioning

confidence: 99%

Inhibition of Growth by Amber Suppressors in Yeast

Liebman

Sherman

1976

Genetics

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Strains of the yeast Saccharomyces cerevisiae that contain highly efficient amber (UAG) suppressors grow poorly on nutrient medium, while normal or nearly normal growth rates are observed when these strains lose the suppressors or when the suppressors are mutated to lower efficiencies. The different growth rates account for the accumulation of mutants with lowered efficiencies in cultures of strains with highly efficient amber suppressors. Genetic analyses indicate that one of the mutations with a lowered efficiency of suppression is caused by an intragenic mutation of the amber suppressor. The inhibition of growth caused by excessive suppression is expected to be exacerbated when appropriate suppressors are combined together in haploid cells if two suppressors act with a greater efficiency than a single suppressor. Such retardation of growth is observed with combinations of two UAA (ochre) suppressors (Gilmore 1967) and with combinations of two UAG suppressors when the efficiencies of each of the suppressors are within a critical range. In contrast, combinations of a UAA suppressor and a UAG suppressor do not affect growth rate. Apparently while either excessive UAA or excessive UAG suppression is deleterious to yeast, a moderate level of simultaneous UAA and UAG suppression is not.

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Section: Discussionmentioning

confidence: 99%

Inhibition of Growth by Amber Suppressors in Yeast

Liebman

Sherman

1976

Genetics

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“…It was recently demonstrated that serine is inserted by the highly efficient UAG suppressor SUP-RLI, which is lethal in haploids but which can be maintained in the heterozygous condition ( BRANDRISS, STEWART, SHERMAN and BOTSTEIN, manuscript in preparation). Chromosome mapping studies have established that this suppressor is not an allele of the serine-inserting suppressor SUQS (BRANDRISS, SOLL and BOTSTEIN 1975;LIEBMAN, STEWART and SHERMAN 1975a).…”

Section: Discussionmentioning

confidence: 99%

Isolation and Characterization of Amber Suppressors in Yeast

1976

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Nonsense suppressors were obtained in a haploid yeast strain containing eight nutritional mutations, that are assumed to be amber or ochre, and the cyc1-179 amber mutation that has a UAG codon corresponding to position 9 in iso-1-cytochrome c. Previous studies established that the biosynthesis and function of iso-1-cytochrome c is compatible with replacements at position 9 of amino acids having widely different structures (Stewart and Sherman 1972). UV-induced revertants, selected on media requiring the reversion of one or two of the amber nutritional markers, were presumed to contain a suppressor if there was the unselected reversion of at least one other marker. The 1088 suppressors that were isolated could be divided into 78 phenotypic classes. Only 43 suppressors of three classes caused the production of more than 50% of the normal amount of iso-1-cytochrome c in the cyc1-179 strain. Genetic analyses indicated that all of these highly efficient amber suppressors are allelic to one or another of the eight suppressors which cause the insertion of tyrosine at ochre (UAA) codons (Gilmore, Stewart and Sherman 1971). Furthermore, only tyrosine has been identified at position 9 in iso-1-cytochrome cin cyc1-179 strains suppressed with these efficient amber suppressors.

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“…Cells completely defective in tRNA splicing should not be viable, since all eight tRNATYr genes contain introns (7,10). Furthermore, the gene for the tRNA that decodes the rarely used serine codon UCG also contains an intron; loss of this gene function is lethal (3,5,6). Thus, losi cells appear to be capable of properly splicing precursor tRNAs, but perhaps at a slower rate than wild-type cells.…”

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Cloning and Characterization of LOS1, a Saccharomyces cerevisiae Gene That Affects tRNA Splicing

Hurt

Wang

Lin

et al. 1987

Molecular and Cellular Biology

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Saccharomyces cerevisiae strains carrying los1-1 mutations are defective in tRNA processing; at 37 degrees C, such strains accumulate tRNA precursors which have mature 5' and 3' ends but contain intervening sequences. Strains bearing los1-1 and an intron-containing ochre-suppressing tRNA gene, SUP4(0), also fail to suppress the ochre mutations ade2-1(0) and can1-100(0) at 34 degrees C. To understand the role of the LOS1 product in tRNA splicing, we initiated a molecular study of the LOS1 gene. Two plasmids, YEpLOS1 and YCpLOS1, that complement the los1-1 phenotype were isolated from the YEp24 and YCp50 libraries, respectively. YEpLOS1 and YCpLOS1 had overlapping restriction maps, indicating that the DNA in the overlapping segment could complement los1-1 when present in multiple or single copy. Integration of plasmid DNA at the LOS1 locus confirmed that these clones contained authentic LOS1 sequences. Southern analyses showed that LOS1 is a single copy gene. The locations of the LOS1 gene within YEpLOS1 and YCpLOS1 were determined by deletion and gamma-delta mapping. Two genomic disruptions of the LOS1 gene were constructed, i.e., an insertion of a 1.2-kilobase fragment carrying the yeast URA3 gene, los1::URA3, and a 2.4-kilobase deletion from the LOS1 gene, los1-delta V. Disruption or deletion of most of the LOS1 gene was not lethal; cells carrying the disrupted los1 alleles were viable and had phenotypes similar to those of cells carrying the los1-1 allele. Thus, it appears that the los1 gene product expedites tRNA splicing at elevated temperatures but is not essential for this process.

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Recessive Lethal Amber Suppressors in Yeast

Cited by 33 publications

References 17 publications

Inhibition of Growth by Amber Suppressors in Yeast

Inhibition of Growth by Amber Suppressors in Yeast

Isolation and Characterization of Amber Suppressors in Yeast

Cloning and Characterization of LOS1, a Saccharomyces cerevisiae Gene That Affects tRNA Splicing

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