Translational regulation of the spc operon in Escherichia coli

Cerretti, Douglas Pat; Mattheakis, Larry; Kearney, Kevin R.; Vu, Loan; Nomura, Masayasu

doi:10.1016/0022-2836(88)90578-5

Cited by 78 publications

(37 citation statements)

References 49 publications

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“…Some other translational regulators follow a similar strategy, selectively inhibiting the translation of internal genes carried by a polycistronic mRNA. This is the case of some E. coli ribosomal proteins (43,44) and of several small antisense RNAs (45,46).…”

Section: Discussionmentioning

confidence: 99%

The Crc Global Regulator Inhibits the Pseudomonas putida pWW0 Toluene/Xylene Assimilation Pathway by Repressing the Translation of Regulatory and Structural Genes

Moreno

Fonseca²,

Rojo

2010

Journal of Biological Chemistry

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In Pseudomonas putida, the expression of the pWW0 plasmid genes for the toluene/xylene assimilation pathway (the TOL pathway) is subject to complex regulation in response to environmental and physiological signals. This includes strong inhibition via catabolite repression, elicited by the carbon sources that the cells prefer to hydrocarbons. The Crc protein, a global regulator that controls carbon flow in pseudomonads, has an important role in this inhibition. Crc is a translational repressor that regulates the TOL genes, but how it does this has remained unknown. This study reports that Crc binds to sites located at the translation initiation regions of the mRNAs coding for XylR and XylS, two specific transcription activators of the TOL genes. Unexpectedly, eight additional Crc binding sites were found overlapping the translation initiation sites of genes coding for several enzymes of the pathway, all encoded within two polycistronic mRNAs. Evidence is provided supporting the idea that these sites are functional. This implies that Crc can differentially modulate the expression of particular genes within polycistronic mRNAs. It is proposed that Crc controls TOL genes in two ways. First, Crc inhibits the translation of the XylR and XylS regulators, thereby reducing the transcription of all TOL pathway genes. Second, Crc inhibits the translation of specific structural genes of the pathway, acting mainly on proteins involved in the first steps of toluene assimilation. This ensures a rapid inhibitory response that reduces the expression of the toluene/ xylene degradation proteins when preferred carbon sources become available.

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Section: Discussionmentioning

confidence: 99%

The Crc Global Regulator Inhibits the Pseudomonas putida pWW0 Toluene/Xylene Assimilation Pathway by Repressing the Translation of Regulatory and Structural Genes

Moreno

Fonseca²,

Rojo

2010

Journal of Biological Chemistry

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“…Details are described in ref. 6 (10). The rate of transcription of these operons increased %2-fold in a strain carrying an extra copy of these operons as a transducing phage, Aspc2, but the rate of synthesis of ribosomal proteins encoded by these operons, including L14-L24, did not increase to any significant extent.…”

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confidence: 99%

“…§ S8 was identified as the operon-specific translational repressor (4,5). Its target site was located at the beginning of the third gene (encoding L5) by both in vivo and in vitro experiments (6). While the regulation of distal genes (those for S14 to L15) has been shown (7) to be achieved by S8 indirectly through translational coupling of distal genes with the L5 gene, the regulation ofthe proximal two genes has remained unclear.…”

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confidence: 99%

Retroregulation of the synthesis of ribosomal proteins L14 and L24 by feedback repressor S8 in Escherichia coli.

Mattheakis

Sor

et al. 1989

Proc. Natl. Acad. Sci. U.S.A.

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Previous studies on regulation of the spc operon containing genes for ribosomal proteins have shown that S8, encoded by the fifth gene of the operon in Escherichia coli, is a translational repressor and regulates the synthesis of the third gene product (LS) and distal gene products by acting at a site near the L5 mRNA translation initiation site. We have now shown that S8 also regulates the synthesis of the first and second gene products (L14 and L24) of the operon by acting at the same mRNA target site-that is, the site located distal to sites coding for L14 and L24-and that mRNA degradation is involved in this retroregulation. It was shown that single base substitutions in the target site, which abolish repression of the synthesis of L5 and L5-distal gene products by S8, also cause derepression of L14-L24 synthesis. Inhibition of L14-L24 synthesis by S8 was also shown by overproducing S8 in trans from a plasmid carrying the S8 gene under lac promoter/ operator control. A strain carrying temperature-sensitive mutations in genes for polynucleotide phosphorylase and RNase II was found upon shift to nonpermissive temperature to show higher differential synthesis rates of L14-L24 (and L5) relative to those of several L5-distal spc operon gene products. We suggest that repression of distal ribosomal protein synthesis by S8 triggers nucleolytic cleavage of spc operon mRNA, followed by mRNA degradation by these 3'-to 5'-exonucleases, which is then responsible for inhibition of L14-L24 synthesis.It is well established that the synthesis of many ribosomal proteins in Escherichia coli is regulated by a posttranscriptional feedback mechanism using certain key ribosomal proteins as translational repressors and that this feedback mechanism is important for coordination ofribosomal protein synthesis to rRNA synthesis (for reviews, see refs. 1-3).The spc operon contains the genes for ribosomal proteins L14, L24, L5, S14, S8, L6, L18, S5, L30, and L15 in that order (see Fig. 1). § S8 was identified as the operon-specific translational repressor (4, 5). Its target site was located at the beginning of the third gene (encoding L5) by both in vivo and in vitro experiments (6). While the regulation of distal genes (those for S14 to L15) has been shown (7) to be achieved by S8 indirectly through translational coupling of distal genes with the L5 gene, the regulation ofthe proximal two genes has remained unclear. We now report the presence of a novel mechanism, retroregulation by a feedback repressor ribosomal protein, for the regulation of the synthesis of L14 and L24 ("L14-L24 synthesis"). We show that L14-L24 synthesis is regulated by S8 acting at the same target site as that used for translational regulation of the L5 gene and distal cistrons, -and that this retroregulation probably involves degradation of L14-L24 mRNA by 3'-to 5'-exonucleases. MATERIALS AND METHODSTransducing phage Aspc2 and plasmids pNO1018 and pNO2829 (and its DC7 mutant derivative) are described in refs. 5,6, and 8, respectively, and are shown in Fig...

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“…Although a few other ribosomal determinants have been identified, r-protein gene organization and expression have not been well characterized (7-10, 20, 21). Interestingly, the organization and transcriptional regulation of r-protein operons appear to be well conserved among eubacteria; however, their regulation among evolutionary distant species remains unelucidated (15).Recently, we reported the cloning and sequencing of the r-protein CtrL6e from C. trachomatis, which is structurally and functionally homologous to Escherichia coli r-protein EcoL6 (13 (6,31). In Bacillus subtilis and Thennus aquaticus, however, no structure resembling an S8 translational repressor has been identified, suggesting some different mechanism of transcriptional regulation (15, 18).…”

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“…Recently, we reported the cloning and sequencing of the r-protein CtrL6e from C. trachomatis, which is structurally and functionally homologous to Escherichia coli r-protein EcoL6 (13 (6,31). In Bacillus subtilis and Thennus aquaticus, however, no structure resembling an S8 translational repressor has been identified, suggesting some different mechanism of transcriptional regulation (15, 18).…”

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confidence: 99%

Cloning and sequence analysis of the Chlamydia trachomatis spc ribosomal protein gene cluster

et al. 1992

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We identified and sequenced a segment of Chlamydia trachomatis chromosomal DNA that shows homology to the Escherichia coli spc and distal region of the S10 ribosomal protein (r-protein) operons. Its sequence revealed a high degree of nucleotide and operon context conservation with the E. coli r-protein genes. The C. trachomatis spc operon contains the r-protein genes for L14, L24, L5, S8, L6, L18, S5, L15, and Sec Y along with the genes for r-proteins L16, L29, and S17 of the S10 operon. The two operons are separated by a 16-bp intragenic region which contains no transcription signals. However, a putative promoter for the transcription of the spc operon was found 162 nucleotides upstream of the CtrL14e start site; it revealed significant homology to the E. coli consensus promoter sequences. Interestingly, our results indicate the absence of any structure resembling an EcoS8 regulatory target site on C. trachomatis spc mRNA in spite of significant amino acid identity between E. coli and C. trachomatis r-proteins. Also, the intrinsic aminoglycoside resistance in C. trachomatis is unlikely to be mediated by CtrL6e since E. coli expressing CtrL6e remained susceptible to gentamicin (MIC < 0.5 ,ug/ml).Chlamydia trachomatis infections represent major public health problems in both developing and industrialized countries (30). Chlamydia species have evolved a complex and unique developmental cycle which involves two distinct forms: the small (0.2 to 0.3 ,um) extracellular, rigid elementary bodies and the large (1 ,um) intracellular, fragile reticulate bodies (44). The genetics of chlamydial regulation is largely undefined, mainly because of the lack of any convenient system for gene transfer and also because of the paucity of information about the signals and machinery that govern gene expression.Ribosomes constitute the protein-synthesizing machinery of both prokaryotes and eukaryotes. The entire prokaryotic ribosome comprises three rRNAs with sedimentation coefficients of 23S, 16S, and 5S and approximately 52 ribosomal proteins (r-proteins) that are organized into 19 different operons (26,33). Earlier attempts at characterizing the rRNA from Chlamydia species have met with some success. Tamura and Iwanaga (42) identified 21S, 16S, and 4S rRNA fractions in Chlamydia psittaci; of these, 21S and 16S were more predominant forms in reticulate bodies, whereas 4S predominated in the elementary bodies. Sarov and Becker found similar rRNA species in C. trachomatis (39). On the basis of their 16S rRNA gene sequence, chlamydiae have been identified as eubacterial in origin, related peripherally to planctomyces (45). Although a few other ribosomal determinants have been identified, r-protein gene organization and expression have not been well characterized (7-10, 20, 21). Interestingly, the organization and transcriptional regulation of r-protein operons appear to be well conserved among eubacteria; however, their regulation among evolutionary distant species remains unelucidated (15).Recently, we reported the cloning and sequen...

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Translational regulation of the spc operon in Escherichia coli

Cited by 78 publications

References 49 publications

The Crc Global Regulator Inhibits the Pseudomonas putida pWW0 Toluene/Xylene Assimilation Pathway by Repressing the Translation of Regulatory and Structural Genes

The Crc Global Regulator Inhibits the Pseudomonas putida pWW0 Toluene/Xylene Assimilation Pathway by Repressing the Translation of Regulatory and Structural Genes

Retroregulation of the synthesis of ribosomal proteins L14 and L24 by feedback repressor S8 in Escherichia coli.

Cloning and sequence analysis of the Chlamydia trachomatis spc ribosomal protein gene cluster

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