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  • 1
    Electronic Resource
    Electronic Resource
    Initiation of mRNA translation in prokaryotes (1990)
    s.l. : American Chemical Society
    Biochemistry 29 (1990), S. 5881-5889 
    Details
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/bi00477a001
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  • 2
    Electronic Resource
    Electronic Resource
    Selective expression of the β-subunit of nucleoid-associated protein HU during cold shock in Escherichia coli (2002)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 44 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of Escherichia coli hupA and hupB, the structural genes encoding the most abundant nucleoid-associated proteins HUα and HUβ has been studied during cold shock. This article demonstrates that: (i) transcriptional expression of hupA is blocked following a sudden temperature downshift (from 37°C to 10°C), whereas transcription of hupB from the P2 and P3 promoters is maintained at a constitutive level and is activated de novo from the P4 promoter; (ii) all three hupB mRNAs (transcribed from the three natural promoters P2, P3 and P4) become much more stable than the single hupA transcript; and (iii) the hupB transcripts, unlike that of hupA, are efficiently translated in vivo during cold acclimation and can be actively translated in vitro at low temperature. Taken together, the results indicate that during cold shock the expression of the HUβ subunit is preferentially stimulated and that of HUα repressed, suggesting that an altered HUα to HUβ expression ratio resulting in an increase of HUα/HUβ heterodimers and/or (HUβ)2 homodimers may play an important role during cold adaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02868.x
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  • 3
    Electronic Resource
    Electronic Resource
    Leaderless mRNAs in bacteria: surprises in ribosomal recruitment and translational control (2002)
    Oxford, UK : Blackwell Science Ltd.
    Molecular microbiology 43 (2002), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: It is commonly believed that the translational efficiency of prokaryotic mRNAs is intrinsically determined by both primary and secondary structures of their translational initiation regions. However, for leaderless mRNAs starting with the AUG initiating codon occurring in bacteria, archaea and eukaryotes, there is no evidence for ribosomal recruitment signals downstream of the 5′-terminal AUG that seems to be the only necessary and constant element. Studies in Escherichia coli have brought to light that the ratio of initiation factors IF2 and IF3 plays a decisive role in translation initiation of leaderless mRNA, indicating that the translational efficiency of this mRNA class can be modulated depending on the availability of components of the translational machinery. Recent data suggested that the start codon of bacterial leaderless mRNAs is recognized by a ribosome-IF2-fMet-tRNA complex, an intermediate equivalent to that obligatorily formed during translation initiation in eukaryotes, which points to a conceptual similarity in all initiation pathways. In fact, the faithful translation of lead-erless mRNAs in heterologous systems shows that the ability to translate leaderless mRNAs is an evo-lutionarily conserved function of the translational apparatus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2002.02739.x
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  • 4
    Electronic Resource
    Electronic Resource
    Antagonistic involvement of FIS and H-NS proteins in the transcriptional control of hns expression (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Gel shift and DNase I footprinting experiments showed that Escherichia coli FIS (factor for inversion stimulation) protein binds to at least seven sites in the promoter region of hns. These sites extend from −282 to +25 with two sites, closely flanking the DNA bend located at −150 from the transcriptional startpoint, partly overlapping the H-NS binding sites involved in the transcriptional autorepression of hns. The interplay between FIS, H-NS and the hns promoter region were studied by examining the effects of FIS and H-NS on in vitro transcription of hns–cat fusions, as well as looking at the effect of FIS on preformed complexes containing H-NS and a DNA fragment derived from the hns promoter region. Taken together, our data suggest that in the cell, FIS and H-NS interact with the promoter region of hns and influence their respective interactions (possibly competing for the same binding site), eliciting antagonistic effects so that an interplay between these proteins might contribute to the transcriptional control of hns
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.436961.x
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  • 5
    Electronic Resource
    Electronic Resource
    Translation initiation factor 3 antagonizes authentic start codon selection on leaderless mRNAs (1999)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 31 (1999), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In this study, we have examined the influence of initiation factors on translation initiation of leaderless mRNAs whose 5′-terminal residues are the A of the AUG initiating codon. A 1:1 ratio of initiation factors to ribosomes abolished ternary complex formation at the authentic start codon of different leaderless mRNAs. Supporting this observation, in vitro translation assays using limiting ribosome concentrations with competing leaderless λcI and Escherichia coli ompA mRNAs, the latter containing a canonical ribosome binding site, revealed reduced cI synthesis relative to OmpA in the presence of added initiation factors. Using in vitro toeprinting and in vitro translation assays, we show that this effect can be attributed to IF3. Moreover, in vivo studies revealed that the translational efficiency of a leaderless reporter gene is decreased with increased IF3 levels. These studies are corroborated by the observed increased translational efficiency of a leaderless reporter construct in an infC mutant strain unable to discriminate against non-standard start codons. These results suggest that, in the absence of a leader or a Shine–Dalgarno sequence, the function(s) of IF3 limits stable 30S ternary complex formation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1999.01147.x
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  • 6
    Electronic Resource
    Electronic Resource
    Expression of the gene encoding the major bacterial nucleoid protein H-NS is subject to transcriptional auto-repression (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 10 (1993), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Expression of a promoterless cat gene fused to a DNA fragment of approximately 400 bp, beginning at –313 of Escherichia coli hns, was significantly repressed in E. coli and Salmonella typhimurium strains with wild-type hns but not in mutants carrying hns alleles. CAT expression from fusions containing a shorter (110 bp) segment of hns was essentially unaffected in the same genetic backgrounds. The stage of growth was found to influence the extent of repression which was maximum (approximately 75%) in mid-log cultures and negligible in cells entering the stationary phase. The level of repression in early-log phase was lower than in mid-log phase cultures, probably because of the presence of high levels of Fis protein, which counteracts the H-NS inhibition by stimulating hns transcription. The effects observed in vivo were mirrored by similar results obtained in vitro upon addition of purified H-NS and Fis protein to transcriptional systems programmed with the same hns caf fusions. Electrophoretic gel shift assays, DNase I footprinting and cyclic permutation get analyses revealed that H-NS binds preferentially to the upstream region of its own gene recognizing two rather extended segments of DNA on both sides of a bend centred around –150. When these sites are filled by H-NS, an additional site between approximately –20 and –65, which partly overlaps the promoter, is also occupied. Binding of H-NS to this site is probably the ultimate cause of transcriptional auto-repression.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2958.1993.tb01953.x
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  • 7
    Electronic Resource
    Electronic Resource
    Post-transcriptional regulation of CspA expression in Escherichia coli (1996)
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: The Escherichia coli cspA gene, encoding the major cold-shock protein CspA, was deprived of its natural promoter and placed in an expression vector under the control of the inducible λ PL promoter. After induction of transcription by thermal inactivation of the λ ts repressor, abundant expression of the product (CspA) was obtained if the cells were subsequently incubated at 10°C, but poor expression was obtained if the cells were incubated at 37°C or 30°C. The reason for this differential temperature-dependent expression was investigated and it was found that: (i) the CspA content of the cells decreased more rapidly at 37°C compared to 10°C, regardless of whether transcription was turned off by addition of rifampicin; (ii) both the chemical and functional half-lives of the cspA transcript were substantially longer at 10°C compared to 37°C; (iii) S30 extracts as well as 70S ribosomes prepared from cold-shocked cells translated CspA mRNA (but not phage MS2 RNA) more efficiently than equivalent extracts or ribosomes obtained from control cells grown at 37°C; and (iv) purified CspA stimulated CspA mRNA translation. Overall, these results indicate that a selective modification of the cold-shocked translational apparatus favouring translation of CspA mRNA, and an increased stability of this mRNA at low temperature, may play an important role in the induction of cspA expression during cold shock.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.362897.x
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  • 8
    Electronic Resource
    Electronic Resource
    The virF promoter in Shigella: more than just a curved DNA stretch (2004)
    Oxford, UK : Blackwell Science Ltd
    Molecular microbiology 51 (2004), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: In the human enteropathogen Shigella transcription of virF, the primary regulator of the invasion functions, is strictly temperature-dependent and is antagonistically mediated by H-NS and FIS, which bind to specific sites on the virF promoter. Here we report on the relevance of DNA geometry to the themoregulation of virF and demonstrate that the virF promoter hosts a major DNA bend halfway between two H-NS sites. The bent region has been mutagenized in vitro to mimic temperature-induced changes of DNA curvature. Functional analysis of curvature mutants and of promoter constructs in which the two H-NS sites are phased-out by a half–helix turn reveals that modifying the spatial relationships between these sites severely affects the interaction of H-NS with the virF promoter, as well as its in vivo and in vitro temperature-dependent activity. The role of promoter curvature as thermosensor is also compatible with the present observation that, with increasing temperature, the virF bending centre moves downstream at a rate having its maximum around the transition temperature, abruptly unmasking a binding site for the transcriptional activator FIS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.2003.03848.x
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  • 9
    Electronic Resource
    Electronic Resource
    Conformational transition of initiation factor 2 from the GTP- to GDP-bound state visualized on the ribosome (2005)
    [s.l.] : Nature Publishing Group
    Nature structural & molecular biology 12 (2005), S. 1145-1149 
    Details
    ISSN: 1545-9985
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Initiation of protein synthesis is a universally conserved event that requires initiation factors IF1, IF2 and IF3 in prokaryotes. IF2 is a GTPase essential for binding initiator transfer RNA to the 30S ribosomal subunit and recruiting the 50S subunit into the 70S initiation complex. We present two ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nsmb1012
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  • 10
    Electronic Resource
    Electronic Resource
    Preliminary characterization by X-ray diffraction and Raman spectroscopy of a crystalline complex of Bacillus stearothermophilus initiation factor 2 C-domain and fMet-tRNAfMet (1999)
    Copenhagen : International Union of Crystallography (IUCr)
    Acta crystallographica 55 (1999), S. 712-716 
    Details
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: Bacillus stearothermophilus translation initiation factor 2 (IF2) specifically binds initiator fMet-tRNAfMet and positions it into the ribosomal peptidyl site in the course of the initiation of protein biosynthesis. The isolated C-terminal domain of IF2 is capable of binding fMet-tRNAfMet, as shown by RNase A and hydrolysis protection experiments. In the presence of fMet-tRNAfMet, the IF2 C-domain yielded orthorhombic crystals of space group I222 (I212121) diffracting to 3.4 Å resolution. The existence of equimolar amounts of tRNA and protein in the crystals was proven by Raman spectroscopy. The observed unit cell suggests the presence of two IF2 C-domain–fMet-tRNAfMet complexes per asymmetric unit of the crystal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0907444998014577
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