Biomedical subjects

Y O Chernoff

Publications and source records attributed to Y O Chernoff.

27 records · Page 2Linked to original sources

PubMed1993

The 5-aminoimidazole ribonucleotide-carboxylase structural gene of the methylotrophic yeast Pichia methanolica: cloning, sequencing and homology analysis.

The ADE1 gene of the yeast Pichia methanolica encodes phosphoribosyl-5-aminoimidazole-carboxylase (AIRC, EC 4.1.1.21), which is involved in purine biosynthesis. The gene was cloned by complementation of an ade2 mutation in Saccharomyces cerevisiae and a 3077 nucleotide DNA fragment was sequenced. The sequence possessed a single open reading frame, corresponding to a 543 amino acid sequence. The sequence of this putative protein has been compared to the proteins of homologous genes from S. cerevisiae, Schizosaccharomyces pombe, Escherichia coli, chicken and man. The analysis revealed remarkable homology between yeast AIRCs, while for other proteins homology was limited to defined regions.

Amino Acid Sequence↗

PubMed1993

Multicopy SUP35 gene induces de-novo appearance of psi-like factors in the yeast Saccharomyces cerevisiae.

Previously, we have shown that plasmid-mediated multiplication of Saccharomyces cerevisiae wild-type SUP35 gene leads to omnipotent suppression and is incompatible with psi-factor, which is an endogenous extrachromosomal suppressor. Here, we describe a frequent de-novo appearance of psi-like factors in mitotic progeny of yeast transformants containing multicopy SUP35 gene.

DNA, Fungal↗

PubMed1993

Deletion analysis of the SUP35 gene of the yeast Saccharomyces cerevisiae reveals two non-overlapping functional regions in the encoded protein.

SUP35 is an omnipotent suppressor gene of Saccharomyces cerevisiae coding for a protein consisting of a C-terminal part similar to the elongation factor EF-1 alpha and a unique N-terminal sequence of 253 amino acids. Twelve truncated versions of the SUP35 gene were generated by the deletion of fragments internal to the coding sequence. Functional studies of these deletion mutants showed that: (i) only the EF-1 alpha-like C-terminal part of the Sup35 protein is essential for the cell viability; (ii) overexpression of either the N-terminal part of the Sup35 protein or the full-length Sup35 protein decreases translational fidelity, resulting in omnipotent suppression and reduced growth of [psi+] strains; (iii) expression of the C-terminal part of the Sup35 protein generates an antisuppressor phenotype; and (iv) both the N- or C-terminal segments of the Sup35 protein can bind to 80S ribosomes. Thus, the data obtained define two domains within the Sup35 protein which are responsible for different functions.

Fungal Proteins↗

PubMed1992

Dosage-dependent translational suppression in yeast Saccharomyces cerevisiae.

The overexpression of SUP35 (SUP2) wild-type gene, caused by increase of its copy number, induces an omnipotent suppression similar to the phenotype of mutants for this gene. The effect of extra-SUP35 was detected for moderate or even low copy number. Moreover, overdosage of the fragment including only the 5'-flanking region and N-terminal 100 bp of protein-coding sequence of SUP35 leads to allosuppression. Multi-SUP35 gene was also incompatible with extrachromosomal suppressor factor psi, presumably because of a high level of mistranslation. The suppressor effect caused by overdosage of another gene, SUP45 (SUP1), is much lower and can be detected only for one construction which is derived from high copy number plasmid. Suppression induced by extra-SUP35 and especially by extra-SUP45 is affected by the cell environment. A model predicting that the balance of gene products is a key for regulation of translational fidelity is discussed.

DNA Replication↗

PubMed1992

Conservative system for dosage-dependent modulation of translational fidelity in eukaryotes.

Variations in dosage of some genes can alter the level of translational fidelity. The Saccharomyces cerevisiae genes that act as dosage-dependent suppressors and/or modulators of suppression, are the following: some tRNA genes (for example, tRNA(Gln)) inducing readthrough by mispairing; genes coding for either translational elongation factor or other proteins taking part in translation; and some genes of unknown function. We suggest that the SUP35 protein is a factor which may play a major role in balance-dependent regulation of translational fidelity. Homologues of this genes have been identified in other yeast genera (Pichia), green algae (Chlamydomonas) and various animals including man. No homologies have been found in the polychaeta (Nereis) or in insects (Drosophila). Rates of evolution differ for two separate parts of the genes; the N-terminal part, which is important for ambiguous translation in Saccharomyces, is markedly variable in the organisms tested. However, the C-terminal part which is required for yeast viability has a common origin but a separate evolution from that of the EF-Tu protein family.

Animals↗

PubMed1991

Interactions between chromosomal omnipotent suppressors and extrachromosomal effectors in Saccharomyces cerevisiae.

Chromosomal omnipotent suppressor mutations recovered in psi+ strains of Saccharomyces cerevisiae were brought into psi- cytoplasm. SUP46, SUP138 and SUP139 acted as dominant omnipotent suppressors in the psi- cytoplasm though their suppressor activity was substantially reduced. SUP46 and SUP138 conferred recessive thermosensitivity and antibiotic sensitivity in psi- cytoplasm as in psi+ cytoplasm. On the other hand, sup111 through sup115, which acted as recessive omnipotent suppressors in the psi+ cytoplasm, manifested no, or very low, suppressor activity in the psi- cytoplasm. They, however, still enhanced the efficiency of the SUP29 tRNA suppressor in psi- cytoplasm. A multicopy plasmid carrying the wild-type SUP35 gene enhanced the efficiency of sup111 in psi- cytoplasm.

Extrachromosomal Inheritance↗

PubMed1988

Precise excision of bacterial transposon Tn5 in yeast.

We have demonstrated that precise excision of bacterial transposon Tn5 can occur in the yeast, Saccharomyces cerevisiae. Tn5 insertions in the yeast gene LYS2 were generated by transposon mutagenesis made in Escherichia coli by means of a lambda::Tn5 vector. Nine insertions of Tn5 into the structural part of the yeast LYS2 gene situated in a shuttle episomal plasmid were selected. All the plasmids with a Tn5 insertion were used to transform yeast strains carrying a deletion of the entire LYS2 gene or a deletion of the part of LYS2 overlapping the point of insertion. All insertions inactivated the LYS2 gene and were able to revert with low (about 10(-8) frequencies to lysine prototrophy. Restriction analysis of revertant plasmids revealed them to be indistinguishable from the original plasmid without Tn5 insertion. DNA sequencing of the regions containing the points of insertions, made for two revertants, proved that Tn5 excision was completely precise.

DNA Transposable Elements↗

PubMedDate not supplied

Divergence and conservation of SUP2 (SUP35) gene of yeast Pichia pinus and Saccharomyces cerevisiae.

SUP2 (SUP35) is an omnipotent suppressor gene, coding for an EF-1 alpha-like protein factor, intimately involved in the control of translational accuracy in yeast Saccharomyces cerevisiae. In the present study a SUP2 gene analogue from yeast Pichia pinus was isolated by complementation of the temperature-sensitive sup2 mutation of S. cerevisiae. The nucleotide sequence of the SUP2 gene of P. pinus codes for a protein of 82.4 kDa, exceeding the Sup2 protein of S. cerevisiae by 6 kDa. Like the SUP2 gene product of S. cerevisiae, the Sup2 protein of P. pinus represents a fusion of a unique N-terminal part and a region homologous to EF-1 alpha. The comparison of amino acid sequences of the Sup2 proteins reveals high conservation (76%) of the C-terminal region and low conservation (36%) of the N-terminal part where, in addition, the homologous correspondence is ambiguous. Proteins related to the Sup2 of S. cerevisiae were found in P. pinus and some other yeast species by the immunoblotting technique. The relation between the evolutionary conservation of different regions of the Sup2 protein and their functional significance is discussed.

Amino Acid Sequence↗

PubMedDate not supplied

The accuracy center of a eukaryotic ribosome.

Mutations in yeast ribosomal proteins and ribosomal RNAs have been shown to affect translational fidelity. These mutations include: proteins homologous to Escherichia coli's S4, S5, and S12; a eukaryote specific ribosomal protein; yeast ribosomal rRNA alterations at positions corresponding to 517, 912, and 1054 in 16S E. coli rRNA and to 2658 in the sarcin-ricin domain of 23S E. coli rRNA. Overall there appears to be a remarkable conservation of the accuracy center throughout evolution.

Fungal Proteins↗