A rare tRNA-Arg(CCU) that regulates Ty1 element ribosomal frameshifting is essential for Ty1 retrotransposition in Saccharomyces cerevisiae.
Translation of the yeast retrotransposon Ty1 TYA1(gag)-TYB1(pol) gene occurs by a +1 ribosomal frameshifting event at the sequence CUU AGG C. Because overexpression of a low abundance tRNA-Arg(CCU) encoded by the HSX1 gene resulted in a reduction in Ty1 frameshifting, it was suggested that a translational pause at the AGG-Arg codon is required for optimum frameshifting. The present work shows that the absence of tRNA-Arg(CCU) affects Ty1 transposition, translational frameshifting, and accumulation of mature TYB1 proteins. Transposition of genetically tagged Ty1 elements decreases at least 50-fold and translational frameshifting increases 3-17-fold in cells lacking tRNA-Arg(CCU). Accumulation of Ty1-integrase and Ty1-reverse transcriptase/ribonuclease H is defective in an hsx1 mutant. The defect in Ty1 transposition is complemented by the wild-type HSX1 gene or a mutant tRNA-Arg(UCU) gene containing a C for T substitution in the first position of the anticodon. Overexpression of TYA1 stimulates Ty1 transposition 50-fold above wild-type levels when the level of transposition is compared in isogenic hsx1 and HSX1 strains. Thus, the HSX1 gene determines the ratio of the TYA1 to TYA1-TYB1 precursors required for protein processing or stability, and keeps expression of TYB1 a rate-limiting step in the retrotransposition cycle.
Kawakami
K
K
Department of Tumor Biology, University of Tokyo, Japan.
Pande
S
S
Faiola
B
B
Moore
D P
DP
Boeke
J D
JD
Farabaugh
P J
PJ
Strathern
J N
JN
Nakamura
Y
Y
Garfinkel
D J
DJ
D001483:Base Sequence; D017931:DNA Primers; D004251:DNA Transposable Elements; D004171:Diploidy; D016368:Frameshift Mutation; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal; D015750:Genes, gag; D015751:Genes, pol; D005838:Genotype; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012331:RNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D012347:RNA, Transfer, Arg / Q000235:genetics*; D016364:Reading Frames; D012190:Retroviridae / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development
D017931:DNA Primers; D004251:DNA Transposable Elements; D012331:RNA, Fungal; D012347:RNA, Transfer, Arg