Belcourt M F, Farabaugh P J
Department of Microbiology University of Connecticut Health Center Farmington 06032.
Cell. 1990 Jul 27;62(2):339-52. doi: 10.1016/0092-8674(90)90371-k.
Ribosomal frameshifting regulates expression of the TYB gene of yeast Ty retrotransposons. We previously demonstrated that a 14 nucleotide sequence conserved between two families of Ty elements was necessary and sufficient to support ribosomal frameshifting. This work demonstrates that only 7 of these 14 nucleotides are needed for normal levels of frameshifting. Any change to the sequence CUU-AGG-C drastically reduces frameshifting; this suggests that two specific tRNAs, tRNA(UAGLeu) and tRNA(CCUArg), are involved in the event. Our tRNA overproduction data suggest that a leucyl-tRNA, probably tRNA(UAGLeu), an unusual leucine isoacceptor that recognizes all six leucine codons, slips from CUU-Leu onto UUA-Leu (in the +1 reading frame) during a translational pause at the AGG-Arg codon induced by the low availability of tRNA(CCUArg), encoded by a single-copy essential gene. Frameshifting is also directional and reading frame specific. Interestingly, frameshifting is inhibited when the "slip" CUU codon is located three codons downstream, but not four or more codons downstream, of the translational initiation codon.
核糖体移码调控酵母Ty逆转座子的TYB基因表达。我们之前证明，在两个Ty元件家族之间保守的一段14个核苷酸的序列对于支持核糖体移码是必要且充分的。这项研究表明，正常水平的移码仅需要这14个核苷酸中的7个。对序列CUU-AGG-C的任何改变都会大幅降低移码；这表明两个特定的tRNA，即tRNA(UAGLeu)和tRNA(CCUArg)，参与了这一过程。我们的tRNA过量表达数据表明，一种亮氨酰-tRNA，可能是tRNA(UAGLeu)，一种能识别所有六个亮氨酸密码子的不寻常亮氨酸同工受体，在由单拷贝必需基因编码的tRNA(CCUArg)可用性较低所诱导的AGG-Arg密码子处的翻译暂停期间，从CUU-Leu滑向UUA-Leu（在+1阅读框中）。移码也是有方向性的且具有阅读框特异性。有趣的是，当“滑读”的CUU密码子位于翻译起始密码子下游三个密码子处时，移码受到抑制，但位于下游四个或更多密码子处时则不受抑制。
