scholarly journals Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1.

1984 ◽  
Vol 4 (9) ◽  
pp. 1747-1753 ◽  
Author(s):  
S S Sommer ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Size Variation ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Enhanced Degradation

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

Double-stranded RNAs that encode killer toxins in Saccharomyces cerevisiae: unstable size of M double-stranded RNA and inhibition of M2 replication by M1

1984 ◽  
Vol 4 (9) ◽  
pp. 1747-1753
Author(s):  
S S Sommer ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Size Variation ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Enhanced Degradation

The sizes of M1 and M2 (but not L) change rapidly with growth, varying by perhaps as much as 33%. Size variation is seen within 76 generations. In addition, the exclusion of M2 by M1 or L-A-E [( EXL]) is mediated by inhibition of replication or segregation, not by enhanced degradation of preexisting molecules.

Ustilago maydis KP6 killer toxin: structure, expression in Saccharomyces cerevisiae, and relationship to other cellular toxins

1990 ◽  
Vol 10 (4) ◽  
pp. 1373-1381
Author(s):  
J Tao ◽  
I Ginsberg ◽  
N Banerjee ◽  
W Held ◽  
Y Koltin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fungal Pathogen ◽  
Secretory Pathway ◽  
Rna Virus ◽  
Killer Toxin ◽  
Ustilago Maydis ◽  
Cleavage Sites ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Covalently Linked

There are a number of yeasts that secrete killer toxins, i.e., proteins lethal to sensitive cells of the same or related species. Ustilago maydis, a fungal pathogen of maize, also secretes killer toxins. The best characterized of the U. maydis killer toxins is the KP6 toxin, which consists of two small polypeptides that are not covalently linked. In this work, we show that both are encoded by one segment of the genome of a double-stranded RNA virus. They are synthesized as a preprotoxin that is processed in a manner very similar to that of the Saccharomyces cerevisiae k1 killer toxin, also encoded by a double-strand RNA virus. Active U. maydis KP6 toxin was secreted from S. cerevisiae transformants expressing the KP6 preprotoxin. The two secreted polypeptides were not glycosylated in U. maydis, but one was glycosylated in S. cerevisiae. Comparison of known and predicted cleavage sites among the five killer toxins of known sequence established a three-amino-acid specificity for a KEX2-like enzyme and predicted a new, undescribed processing enzyme in the secretory pathway in the fungi. The mature KP6 toxin polypeptides had hydrophobicity profiles similar to those of other known cellular toxins.

scholarly journals Ustilago maydis KP6 killer toxin: structure, expression in Saccharomyces cerevisiae, and relationship to other cellular toxins.

1990 ◽  
Vol 10 (4) ◽  
pp. 1373-1381 ◽  
Author(s):  
J Tao ◽  
I Ginsberg ◽  
N Banerjee ◽  
W Held ◽  
Y Koltin ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fungal Pathogen ◽  
Secretory Pathway ◽  
Rna Virus ◽  
Killer Toxin ◽  
Ustilago Maydis ◽  
Cleavage Sites ◽  
Double Stranded Rna ◽  
Killer Toxins ◽  
Covalently Linked

There are a number of yeasts that secrete killer toxins, i.e., proteins lethal to sensitive cells of the same or related species. Ustilago maydis, a fungal pathogen of maize, also secretes killer toxins. The best characterized of the U. maydis killer toxins is the KP6 toxin, which consists of two small polypeptides that are not covalently linked. In this work, we show that both are encoded by one segment of the genome of a double-stranded RNA virus. They are synthesized as a preprotoxin that is processed in a manner very similar to that of the Saccharomyces cerevisiae k1 killer toxin, also encoded by a double-strand RNA virus. Active U. maydis KP6 toxin was secreted from S. cerevisiae transformants expressing the KP6 preprotoxin. The two secreted polypeptides were not glycosylated in U. maydis, but one was glycosylated in S. cerevisiae. Comparison of known and predicted cleavage sites among the five killer toxins of known sequence established a three-amino-acid specificity for a KEX2-like enzyme and predicted a new, undescribed processing enzyme in the secretory pathway in the fungi. The mature KP6 toxin polypeptides had hydrophobicity profiles similar to those of other known cellular toxins.

scholarly journals Tempo and Mode of Ty Element Evolution in Saccharomyces cerevisiae

Genetics ◽  
1999 ◽  
Vol 151 (4) ◽  
pp. 1341-1351 ◽  
Author(s):  
I King Jordan ◽  
John F McDonald
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Negative Selection ◽  
Sequence Variation ◽  
Size Variation ◽  
Sequence Comparisons ◽  
Ty Elements ◽  
Ty Element ◽  
Amino Acid Sequence Variation ◽  
Element Evolution ◽  
High Level

Abstract The Saccharomyces cerevisiae genome contains five families of long terminal repeat (LTR) retrotransposons, Ty1–Ty5. The sequencing of the S. cerevisiae genome provides an unprecedented opportunity to examine the patterns of molecular variation existing among the entire genomic complement of Ty retrotransposons. We report the results of an analysis of the nucleotide and amino acid sequence variation within and between the five Ty element families of the S. cerevisiae genome. Our results indicate that individual Ty element families tend to be highly homogenous in both sequence and size variation. Comparisons of within-element 5′ and 3′ LTR sequences indicate that the vast majority of Ty elements have recently transposed. Furthermore, intrafamily Ty sequence comparisons reveal the action of negative selection on Ty element coding sequences. These results taken together suggest that there is a high level of genomic turnover of S. cerevisiae Ty elements, which is presumably in response to selective pressure to escape host-mediated repression and elimination mechanisms.

Three different M1 RNA-containing viruslike particle types in Saccharomyces cerevisiae: in vitro M1 double-stranded RNA synthesis

1986 ◽  
Vol 6 (5) ◽  
pp. 1552-1561
Author(s):  
R Esteban ◽  
R B Wickner
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Rna Synthesis ◽  
Major Coat Protein ◽  
Double Stranded Rna ◽  
Dsrna Molecule ◽  
Protein Toxin ◽  
New Type ◽  
Viruslike Particles ◽  
M1 Rna

Killer strains of Saccharomyces cerevisiae bear at least two different double-stranded RNAs (dsRNAs) encapsidated in 39-nm viruslike particles (VLPs) of which the major coat protein is coded by the larger RNA (L-A dsRNA). The smaller dsRNA (M1 or M2) encodes an extracellular protein toxin (K1 or K2 toxin). Based on their densities on CsCl gradients, L-A- and M1-containing particles can be separated. Using this method, we detected a new type of M1 dsRNA-containing VLP (M1-H VLP, for heavy) that has a higher density than those previously reported (M1-L VLP, for light). M1-H and M1-L VLPs are present together in the same strains and in all those we tested. M1-H, M1-L, and L-A VLPs all have the same types of proteins in the same approximate proportions, but whereas L-A VLPs and M1-L VLPs have one dsRNA molecule per particle, M1-H VLPs contain two M1 dsRNA molecules per particle. Their RNA polymerase produces mainly plus single strands that are all extruded in the case of M1-H particles but are partially retained inside the M1-L particles to be used later for dsRNA synthesis. We show that M1-H VLPs are formed in vitro from the M1-L VLPs. We also show that the peak of M1 dsRNA synthesis is in fractions lighter than M1-L VLPs, presumably those carrying only a single plus M1 strand. We suggest that VLPs carrying two M1 dsRNAs (each 1.8 kilobases) can exist because the particle is designed to carry one L-A dsRNA (4.5 kilobases).

The coat protein of the yeast double-stranded RNA virus L-A attaches covalently to the cap structure of eukaryotic mRNA

1992 ◽  
Vol 12 (8) ◽  
pp. 3390-3398
Author(s):  
A Blanc ◽  
C Goyer ◽  
N Sonenberg
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Coat Protein ◽  
Translation Initiation ◽  
Rna Virus ◽  
Binding Protein ◽  
Covalent Bond ◽  
Cellular Proteins ◽  
Double Stranded Rna ◽  
Virus Coat ◽  
Drosophila Cells

The eukaryotic mRNA 5' cap structure m7GpppX (where X is any nucleotide) interacts with a number of cellular proteins. Several of these proteins were studied in mammalian, yeast, and drosophila cells and found to be involved in translation initiation. Here we describe a novel cap-binding protein, the coat protein of L-A, a double-stranded RNA virus that is persistently maintained in many Saccharomyces cerevisiae strains. The results also suggest that the coat protein of a related double-stranded RNA virus (L-BC) is likewise a cap-binding protein. Strikingly, in contrast to the cellular cap-binding proteins, the interaction between the L-A virus coat protein and the cap structure is through a covalent bond.

Multiple GCD genes required for repression of GCN4, a transcriptional activator of amino acid biosynthetic genes in Saccharomyces cerevisiae

1986 ◽  
Vol 6 (11) ◽  
pp. 3990-3998
Author(s):  
S Harashima ◽  
A G Hinnebusch
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Amino Acid ◽  
Lacz Gene ◽  
Gene Products ◽  
Wild Type ◽  
Double Mutation ◽  
Double Stranded Rna ◽  
Amino Acid Availability ◽  
Genes Encoding ◽  
New Alleles

GCN4 encodes a positive regulator of multiple unlinked genes encoding amino acid biosynthetic enzymes in Saccharomyces cerevisiae. Expression of GCN4 is coupled to amino acid availability by a control mechanism involving GCD1 as a negative effector and GCN1, GCN2, and GCN3 as positive effectors of GCN4 expression. We used reversion of a gcn2 gcn3 double mutation to isolate new alleles of GCD1 and mutations in four additional GCD genes which we designate GCD10, GCD11, GCD12, and GCD13. All of the mutations lead to constitutive derepression of HIS4 transcription in the absence of the GCN2+ and GCN3+ alleles. By contrast, the gcd mutations require the wild-type GCN4 allele for their derepressing effect, suggesting that each acts by influencing the level of GCN4 activity in the cell. Consistent with this interpretation, mutations in each GCD gene lead to constitutive derepression of a GCN4::lacZ gene fusion. Thus, at least five gene products are required to maintain the normal repressed level of GCN4 expression in nonstarvation conditions. Interestingly, the gcd mutations are pleiotropic and also affect growth rate in nonstarvation conditions. In addition, certain alleles lead to a loss of M double-stranded RNA required for the killer phenotype. This pleiotropy suggests that the GCD gene products contribute to an essential cellular function, in addition to, or in conjunction with, their role in GCN4 regulation.

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