T double-stranded RNA (dsRNA) sequence reveals that T and W dsRNAs form a new RNA family in Saccharomyces cerevisiae. Identification of 23 S RNA as the single-stranded form of T dsRNA.
Some strains of the yeast Saccharomyces cerevisiae harbor a double-stranded RNA (dsRNA) molecule, called T. We obtained T cDNA clones by random priming of denatured T dsRNA followed by reverse transcription. Sequence data of T show that only one strand ((+)-strand) has coding capacity for a protein with 940 amino acids which spans almost the entire length of the molecule (2.9 kilobases). Within this protein we found a sequence pattern characteristic of RNA-dependent RNA polymerases of (+)-strand and double-stranded RNA viruses. Although T has no homology with other dsRNAs found in S. cerevisiae, such as L-A, L-BC, M1, or W, the T-encoded protein shows a high degree of conservation with the W-encoded protein. This conservation extends beyond a region that contains the consensus sequences for RNA-dependent RNA polymerases, suggesting that both T and W are evolutionarily related. With a (+)-strand-specific probe for T we identified 23 S RNA, a new single-stranded RNA (ssRNA) species with a sedimentation coefficient of 23 S. T and 23 S RNA have the same mobility under denaturing conditions with glyoxal, suggesting that 23 S RNA is, in fact, the (+)-single-stranded RNA form of T dsRNA. 23 S RNA synthesis is induced under stress conditions such as heat shock and starvation. The relationship between T and 23 S RNA clearly resembles the one between W and its single-stranded derivative form, 20 S RNA. Thus T and W dsRNAs (and their respective single-stranded species) constitute a new RNA family in S. cerevisiae.
Esteban
L M
LM
Instituto de Microbiología Bioquímica, Consejo Superior de Investigaciones Científicas/Universidad de Salamanca, Spain.
Rodriguez-Cousiño
N
N
Esteban
R
R
D000595:Amino Acid Sequence; D001483:Base Sequence; D015152:Blotting, Northern; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D012330:RNA, Double-Stranded / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics*; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics; D012689:Sequence Homology, Nucleic Acid
D012330:RNA, Double-Stranded; D012331:RNA, Fungal; D004247:DNA; D012321:DNA-Directed RNA Polymerases