The Salmonella typhimurium his operon leader region contains an RNA hairpin-dependent transcription pause site. Mechanistic implications of the effect on pausing of altered RNA hairpins.
The Salmonella typhimurium his leader region contains a well documented transcription attenuator. We report here the results of in vitro transcription studies that characterized a transcription pause site in the his leader region. The pause occurred after synthesis of the first his leader secondary structure (A:B) and immediately preceding addition of G103 to the nascent transcript. RNA polymerase pausing at this site would allow a ribosome synthesizing the his leader peptide to release the paused polymerase and synchronize transcription and translation of the his leader region. The half-life of transcription complexes paused in the his leader was enhanced by NusA, but not guanosine 5'-diphosphate 3'-diphosphate. Nuclease digestion and RNA modeling studies were consistent with a compact three-dimensional structure for the his pause RNA. The half-life of the his leader paused transcription complex was decreased greatly on altered templates in which the C71-G93 base pair was disrupted but was unchanged when the C65-G100 base pair was disrupted. This result is consistent with a model for the structure of paused transcription complexes in which a portion of the RNA:DNA elongation heteroduplex is retained.
Chan
C L
CL
Department of Biology, Washington University, St. Louis, Missouri 63130.
Landick
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D001483:Base Sequence; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology; D006639:Histidine / Q000096:biosynthesis*; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes / Q000138:chemical synthesis; D009876:Operon; D010957:Plasmids; D012329:RNA, Bacterial / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D012486:Salmonella typhimurium / Q000235:genetics*; D014158:Transcription, Genetic
D015345:Oligonucleotide Probes; D012329:RNA, Bacterial; D012333:RNA, Messenger; D006639:Histidine; D012321:DNA-Directed RNA Polymerases