A ribosomal function is necessary for efficient splicing of the T4 phage thymidylate synthase intron in vivo.
Splicing of the group I intron of the T4 thymidylate synthase (td) gene was uncoupled from translation by introducing stop codons in the upstream exon. This resulted in severe splicing deficiency in vivo. Overexpression of a UGA suppressor tRNA partially rescued splicing, suggesting that this in vitro self-splicing intron requires translation for splicing in vivo. Inhibition of translation by the antibiotics chloramphenicol and spectinomycin also resulted in splicing deficiency. Ribosomal protein S12, a protein with RNA chaperone activity, and CYT-18, a protein that stabilizes the three-dimensional structure of group I introns, efficiently rescued the stop codon mutants. We identified a region in the upstream exon that interferes with splicing. Point mutations in this region efficiently alleviate the effect of a nonsense codon. We infer from these results that the ribosome acts as an RNA chaperone to facilitate proper folding of the intron.
Semrad
K
K
Institute of Microbiology and Genetics, Vienna Biocenter, 1030 Wien, Austria.
Schroeder
R
R
D017122:Bacteriophage T4 / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D018388:Codon, Terminator / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000821:virology; D005091:Exons; D005814:Genes, Viral; D007438:Introns; D009154:Mutation; D014176:Protein Biosynthesis; D012326:RNA Splicing / Q000235:genetics; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism*; D013940:Thymidylate Synthase / Q000235:genetics*
D018388:Codon, Terminator; D017931:DNA Primers; D012329:RNA, Bacterial; D012333:RNA, Messenger; D012269:Ribosomal Proteins; C034212:ribosomal protein S12; D013940:Thymidylate Synthase