The leaky UGA termination codon of tobacco rattle virus RNA is suppressed by tobacco chloroplast and cytoplasmic tRNAs(Trp) with CmCA anticodon.
AUTOR(ES)
Zerfass, K
RESUMO
RNA-1 molecules from tobacco rattle virus (TRV) and pea early-browning virus (PEBV), two members of the tobravirus group, have recently been shown to contain internal, in-frame UGA termination codons which are suppressed in vitro. Our results suggest that a UGA stop codon also exists in RNA-1 of pepper ringspot virus (PRV), another tobravirus. UGA suppression may therefore be a universal feature of the expression of tobravirus genomes. We have isolated two natural suppressor tRNAs from uninfected tobacco plants on the basis of their ability to promote readthrough over the leaky UGA codon of TRV RNA-1 in a wheat germ extract depleted of endogenous mRNAs and tRNAs. Their amino acid acceptance and nucleotide sequences identify the two UGA-suppressor tRNAs as chloroplast (chl) and cytoplasmic (cyt) tryptophan-specific tRNAs with the anticodon CmCA. These are the first UGA suppressor tRNAs to be identified in plants. They have several interesting features. (i) Chl tRNA(Trp) suppresses the UGA stop codon more efficiently than cyt tRNA(Trp). (ii) Chl tRNA(Trp) contains an A24:U11 pair in the D-stem as does the mutated Escherichia coli UGA-suppressor tRNA(Trp) which is a more active suppressor than wild-type tRNA(Trp). (iii) The suppressor activity of chl tRNA(Trp) is dependent on the nucleotides surrounding the stop codon because it recognizes UGA in the TRV context but not the UGA in the beta-globin context.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=556927Documentos Relacionados
- Plant mitochondria and chloroplast tRNAsTrp do not suppress the UGA stop codon.
- Heterogeneities in vertebrate tRNAs(Trp) avian retroviruses package only as a primer the tRNA(Trp) lacking modified m2G in position 7.
- Sequence and codon recognition of bean mitochondria and chloroplast tRNAsTrp: evidence for a high degree of homology.
- Molecular mechanism of codon recognition by tRNA species with modified uridine in the first position of the anticodon.
- UGA suppression by normal tRNA Trp in Escherichia coli: codon context effects.