Hypomodification of the wobble base in tRNAGlu, tRNALys, and tRNAGln suppresses the temperature-sensitive phenotype caused by mutant release factor 1.
In Escherichia coli, release factor 1 (RF1) is one of two RFs that mediate termination; it specifically recognizes UAA and UAG stop codons. A mutant allele, prfA1, coding for an RF1 that causes temperature-sensitive (Ts) growth at 42 degrees C, was used to select for temperature-resistant (Ts(+)) suppressors. This study describes one such suppressor that is the result of an IS10 insertion into the cysB gene, giving a Cys(-) phenotype. CysB is a transcription factor regulating the cys regulon, mainly as an activator, which explains the Cys(-) phenotype. We have found that suppression is a consequence of the lost ability to donate sulfur to enzymes involved in the synthesis of thiolated nucleosides. From genetic analyses we conclude that it is the lack of the 5-methylaminomethyl-2-thiouridine (mnm(5)s(2)U) modification of the wobble base of tRNA(Glu), tRNA(Lys), and/or tRNA(Gln) that causes the suppressor phenotype.
Isak
Georgina
G
Department of Genetics, Microbiology, and Toxicology, Stockholm University, Sweden.
Rydén-Aulin
Monica
M
D000483:Alleles; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D018388:Codon, Terminator; D003470:Culture Media; D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006358:Hot Temperature; D010454:Peptide Termination Factors / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D012351:RNA, Transfer, Gln / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012352:RNA, Transfer, Glu / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012357:RNA, Transfer, Lys / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013489:Suppression, Genetic; D013696:Temperature; D013891:Thiouridine / Q000031:analogs & derivatives / Q000378:metabolism
D001426:Bacterial Proteins; D018388:Codon, Terminator; D003470:Culture Media; C062886:CysB protein, Bacteria; D004251:DNA Transposable Elements; D029968:Escherichia coli Proteins; D010454:Peptide Termination Factors; D012351:RNA, Transfer, Gln; D012352:RNA, Transfer, Glu; D012357:RNA, Transfer, Lys; C489005:prfA protein, E coli; D013891:Thiouridine; C011916:5-methylaminomethyl-2-thiouridine