UGA suppression by tRNACmCATrp occurs in diverse virus RNAs due to a limited influence of the codon context.
AUTOR(ES)
Urban, C
RESUMO
We have recently identified chloroplast and cytoplasmic tRNACmCATrp as the first natural UGA suppressor tRNAs in plants. The interaction of these tRNAs with UGA involves a Cm: A mismatch at the first anticodon position. We show here that tRNACmCATrp is incapable of misreading UAA and UAG codons in vitro, implying that unconventional base pairs are not tolerated in the middle anticodon position. Furthermore, we demonstrate that the ability of tRNACmCATrp to promote UGA read-through depends on a quite simple codon context. Part of the sequence surrounding the leaky UGA stop codon in tobacco rattle virus RNA-1 was subcloned into a zein reporter gene and read-through efficiency was measured by translation of RNA transcripts in wheat germ extract. A number of mutations in the codons adjacent to the UGA were introduced by site-directed mutagenesis. It was found that single nucleotide exchanges at either side of the UGA had little effect on read-through efficiency. A pronounced influence on suppression by tRNACmCATrp was seen only if 2 or 3 nt at the 3'-side of the UGA codon had been simultaneously replaced. As a consequence of the flexible codon context accepted by tRNACmCATrp, this tRNA is able to misread the UGA in a number of plant and animal viral RNAs that use translational read-through for expression of some of their genes.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=146097Documentos Relacionados
- UGA suppression by normal tRNA Trp in Escherichia coli: codon context effects.
- Influence of modification next to the anticodon in tRNA on codon context sensitivity of translational suppression and accuracy.
- Codon discrimination and anticodon structural context.
- Plant mitochondria and chloroplast tRNAsTrp do not suppress the UGA stop codon.
- The leaky UGA termination codon of tobacco rattle virus RNA is suppressed by tobacco chloroplast and cytoplasmic tRNAs(Trp) with CmCA anticodon.