Terminator Hairpin (terminator + hairpin)

Distribution by Scientific Domains


Selected Abstracts


Systematic mutagenesis of the thymidine tract of the pyrBI attenuator and its effects on intrinsic transcription termination in Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 1 2007
Katalin Sipos
Summary The pyrBI attenuator of Escherichia coli is an intrinsic transcription terminator composed of DNA with a hyphenated dyad symmetry and an adjacent 8 bp T:A tract (T-tract). These elements specify a G+C-rich terminator hairpin followed by a run of eight uridine residues (U-tract) in the RNA transcript. In this study, we examined the effects on in vivo transcription termination of systematic base substitutions in the T/U-tract of the pyrBI attenuator. We found that these substitutions diminished transcription termination efficiency to varying extents, depending on the nature and position of the substitution. In general, substitutions closer to the dyad symmetry/terminator hairpin exhibited the most significant effects. Additionally, we examined the effects on in vivo transcription termination of mutations that insert from 1 to 4 bases between the terminator hairpin and U-tract specified by the pyrBI attenuator. Our results show an inverse relationship between termination efficiency and the number of bases inserted. The effects of the substitution and insertion mutations on termination efficiency at the pyrBI attenuator were also measured in vitro, which corroborated the in vivo results. Our results are discussed in terms of the current models for intrinsic transcription termination and estimating termination efficiencies at intrinsic terminators of other bacteria. [source]


SsrA-mediated protein tagging in the presence of miscoding drugs and its physiological role in Escherichia coli

GENES TO CELLS, Issue 7 2002
Tatsuhiko Abo
Background: We have shown recently that read-through of a normal stop codon by a suppressor tRNA in specific genes possessing a Rho-independent terminator leads to SsrA-mediated tagging of extended proteins in Escherichia coli cells. Miscoding antibiotics such as kanamycin and streptomycin reduce translational fidelity by binding to the 30S ribosomal subunit. The aim of the present study was to address how miscoding antibiotics affect the read-through of stop codons and SsrA-mediated protein tagging. Results: Miscoding antibiotics caused translational read-through of stop codons when added to the culture medium at sublethal concentrations. Under the same conditions, the drugs enhanced SsrA-mediated tagging of bulk cellular proteins, as observed in cells carrying an ochre suppressor tRNA. Translational read-through products generated from the crp gene in the presence of the antibiotics was efficiently tagged by the SsrA system, presumably because the ribosome reached the 3, end of the mRNA defined by the terminator hairpin. The SsrA-defective cells were more sensitive to the miscoding antibiotics compared to the wild-type cells. Conclusion: We conclude that the SsrA system contributes to the survival of cells by dealing with translational errors in the presence of low concentrations of miscoding antibiotics. [source]


Systematic mutagenesis of the thymidine tract of the pyrBI attenuator and its effects on intrinsic transcription termination in Escherichia coli

MOLECULAR MICROBIOLOGY, Issue 1 2007
Katalin Sipos
Summary The pyrBI attenuator of Escherichia coli is an intrinsic transcription terminator composed of DNA with a hyphenated dyad symmetry and an adjacent 8 bp T:A tract (T-tract). These elements specify a G+C-rich terminator hairpin followed by a run of eight uridine residues (U-tract) in the RNA transcript. In this study, we examined the effects on in vivo transcription termination of systematic base substitutions in the T/U-tract of the pyrBI attenuator. We found that these substitutions diminished transcription termination efficiency to varying extents, depending on the nature and position of the substitution. In general, substitutions closer to the dyad symmetry/terminator hairpin exhibited the most significant effects. Additionally, we examined the effects on in vivo transcription termination of mutations that insert from 1 to 4 bases between the terminator hairpin and U-tract specified by the pyrBI attenuator. Our results show an inverse relationship between termination efficiency and the number of bases inserted. The effects of the substitution and insertion mutations on termination efficiency at the pyrBI attenuator were also measured in vitro, which corroborated the in vivo results. Our results are discussed in terms of the current models for intrinsic transcription termination and estimating termination efficiencies at intrinsic terminators of other bacteria. [source]