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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We demonstrate here that the assembly of the RNase E-based degradosome of Escherichia coli is not required for normal mRNA decay in vivo. In contrast, deletion of the arginine-rich RNA binding site (ARRBS) from the RNase E protein slightly impairs mRNA decay. When both the degradosome scaffold region and the ARRBS are missing, mRNA decay is dramatically slowed, but 9S rRNA processing is almost normal. An extensive RNase E truncation mutation (rnedelta610) had a more pronounced mRNA decay defect at 37 degrees C than the temperature-sensitive rne-1 allele at 44 degrees C. Taken together, these data suggest that the inviability associated with inactivation of RNase E is not related to defects in either mRNA decay or rRNA processing.
Mol Microbiol 2000 Nov
PMID:Analysis of mRNA decay and rRNA processing in Escherichia coli in the absence of RNase E-based degradosome assembly. 1111 19

The effects of erythromycin on the formation of ribosomal subunits were examined in wild-type Escherichia coli cells and in an RNase E mutant strain. Pulse-chase labelling kinetics revealed a reduced rate of 50S subunit formation in both strains compared with 30S synthesis, which was unaffected by the antibiotic. Growth of cells in the presence of [14C]-erythromycin showed drug binding to 50S particles and to a 50S subunit precursor sedimenting at about 30S in sucrose gradients. Antibiotic binding to the precursor correlated with the decline in 50S formation in both strains. Erythromycin binding to the precursor showed the same 1:1 stoichiometry as binding to the 50S particle. Gel electrophoresis of rRNA from antibiotic-treated organisms revealed the presence of both 23S and 5S rRNAs in the 30S region of sucrose gradients. Hybridization with a 23S rRNA-specific probe confirmed the presence of this species of rRNA in the precursor. Eighteen 50S ribosomal proteins were associated with the precursor particle. A model is presented to account for erythromycin inhibition of 50S formation.
Mol Microbiol 2001 May
PMID:Erythromycin inhibition of 50S ribosomal subunit formation in Escherichia coli cells. 1140 2

Expression of thrS, the gene encoding Escherichia coli threonyl-tRNA synthetase, is negatively autoregulated at the translational level. Regulation is due to the binding of threonyl-tRNA synthetase to its own mRNA at a site called the operator, located immediately upstream of the initiation codon. The present work investigates the relationship between regulation and mRNA degradation. We show that two regulatory mutations, which increase thrS expression, cause an increase in the steady-state mRNA concentration. Unexpectedly, however, the half-life of thrS mRNA in the derepressed mutants is equal to that of the wild-type, indicating that mRNA stability is independent of the repression level. All our results can be explained if one assumes that thrS mRNA is either fully translated or immediately degraded. The immediately degraded RNAs are never detected due to their extremely short half-lives, while the fully translated messengers share the same half-lives, irrespective of the mutations. The increase in the steady-state level of thrS mRNA in the derepressed mutants is simply explained by an increase in the population of translated molecules, i.e. those never bound by the repressor, ThrRS. Despite this peculiarity, thrS mRNA degradation seems to follow the classical degradation pathway. Its stability is increased in a strain defective for RNase E, indicating that an endonucleolytic cleavage by this enzyme is the rate-limiting process in degradation. We also observe an accumulation of small fragments corresponding to the 5' end of the message in a strain defective for polynucleotide phosphorylase, indicating that, following the endonucleolytic cleavages, fragments are normally degraded by 3' to 5' exonucleolytic trimming. Although mRNA degradation was suspected to increase the efficiency of translational control based on several considerations, our results indicate that inhibition of mRNA degradation has no effect on the level of repression by ThrRS.
J Mol Biol 2001 Jul 20
PMID:The relationship between translational control and mRNA degradation for the Escherichia coli threonyl-tRNA synthetase gene. 1145 82

The T7 protein encoded by the early gene 0.7 exhibits bifunctional activity. Whereas its C-terminal one-third participates in host transcription shut-off, the N-terminal two-thirds bears a protein kinase ('PK') activity that can phosphorylate a number of host proteins in addition to itself. Here, we show that, when PK is expressed in uninfected Escherichia coli cells, the C-terminal half of RNase E and the associated RNA helicase RhlB are heavily phosphorylated. Meanwhile, a subset of RNase E substrates, including the lac and cat mRNAs synthesized by bacteriophage T7 RNA polymerase (RNAP), are stabilized. These mRNAs are genuinely less stable than their counterparts synthesized by E. coli RNAP, because T7 RNAP outpaces translating ribosomes, creating naked, RNase E-sensitive mRNA stretches behind itself. Thus, PK alleviates this effect of desynchronizing transcription and translation. The relationship between the modification of RNase E and RhlB and these mRNA stabilization effects, which may be relevant to the stability of late T7 mRNAs during infection, is discussed.
Mol Microbiol 2001 Nov
PMID:Bacteriophage T7 protein kinase phosphorylates RNase E and stabilizes mRNAs synthesized by T7 RNA polymerase. 1172 41

The Escherichia coli endonuclease RNase E plays a key role in rRNA maturation and mRNA decay. In particular, it controls the decay of its own mRNA by cleaving it within the 5'-untranslated region (UTR), thereby autoregulating its synthesis. Here, we report that, when the synthesis of an RNase E substrate is artificially induced to high levels in vivo, both the rne mRNA concentration and RNase E synthesis increase abruptly and then decrease to a steady-state level that remains higher than in the absence of induction. Using rne-lacZ fusions that retain or lack the rne 5'UTR, we show that these variations reflect a transient mRNA stabilization mediated by the rne 5'UTR. Finally, by putting RNase E synthesis under the control of an IPTG-controlled promoter, we show that a similar, rne 5'UTR-mediated mRNA stabilization can result from a shortage of RNase E. We conclude that the burst in substrate synthesis has titrated RNase E, stabilizing the rne mRNA by protecting its 5'UTR. However, this stabilization is self-correcting, because it allows the RNase E pool to expand until its mRNA is destabilized again. Thus, autoregulation allows RNase E to adjust its synthesis to that of its substrates, a behaviour that may be common among autoregulated proteins. Incidentally, this adjustment cannot occur when translation is blocked, and we argue that the global mRNA stabilization observed under these conditions originates in part from this defect.
Mol Microbiol 2001 Nov
PMID:Autoregulation allows Escherichia coli RNase E to adjust continuously its synthesis to that of its substrates. 1172 48

The rne gene of Escherichia coli encodes RNase E, an essential endoribonuclease that is involved in both mRNA decay and rRNA processing. Here we present evidence that the gene is transcribed from three promoters: p1, p2 and p3. The p2 and p3 promoters map 34 and 145 nt upstream from the previously characterized rne promoter, p1, generating unusually long 5' UTRs of 395 and 506 nt respectively. Based on promoter-lacZ transcriptional fusions, p1 is a more efficient promoter than either p2 or p3. Low copy number or single copy number vectors carrying rne transcribed from either p1, p2 or p3 alone complement the rne 1018::bla deletion mutation at 30 degrees C, 37 degrees C and 44 degrees C. However, normal autoregulation requires the presence of all three promoters. A comparison among intracellular levels of RNase E, the half-lives of the rpsO, rpsT and rne mRNAs, and growth rates, indicates that the cell contains a considerable excess of RNase E protein. In addition, when the rne transcript is stabilized at low RNase E levels, it is not efficiently translated.
Mol Microbiol 2002 Jan
PMID:RNase E levels in Escherichia coli are controlled by a complex regulatory system that involves transcription of the rne gene from three promoters. 1184 44

The endoribonuclease RNase E plays an important role in RNA processing and degradation in Escherichia coli. The construction of an E. coli strain in which the cellular concentration of RNase E can be precisely controlled has made it possible to examine and quantify the effect of RNase E scarcity on RNA decay, gene regulation and cell growth. These studies show that RNase E participates in a step in the degradation of its RNA substrates that is partially or fully rate-determining. Our data also indicate that E. coli growth requires a cellular RNase E concentration at least 10-20% of normal and that the feedback mechanism that limits overproduction of RNase E is also able to increase its synthesis when its concentration drops below normal. The magnitude of the in-crease in RNA longevity under conditions of RNase E scarcity may be limited by an alternative pathway for RNA degradation. Additional experiments show that RNase E is a stable protein in E. coli. No other E. coli gene product, when either mutated or cloned on a multicopy plasmid, seems to be capable of compensating for an inadequate supply of this essential protein.
Mol Microbiol 2002 Feb
PMID:Consequences of RNase E scarcity in Escherichia coli. 1192 50

The Escherichia coli endoribonucleases RNase E (Rne) and RNase G (Rng) have sequence similarity and broadly similar sequence specificity. Whereas the absence of Rne normally is lethal, we show here that E. coli bacteria that lack the rne gene can be made viable by overexpression of Rng. Rng-complemented cells accumulated precursors of 5S ribosomal RNA (rRNA) and the RNA component of RNase P (i.e. M1 RNA), indicating that normal processing of these Rne-cleaved RNAs was not restored by RNase G; additionally, neither 5S rRNA nor M1 RNA was generated from precursors by RNase G cleavage in vitro. Using DNA microarrays containing 4405 Escherichia coli open reading frames (ORFs), we identified mRNAs whose steady-state level was affected by Rne, Rng or the N-terminal catalytic domain of RNase E. Most transcript species affected by RNase E deficiency were also elevated in an rne deletion mutant complemented by Rng. However, approximately 100 mRNAs that accumulated in Rne-deficient cells were decreased by rng-complemention, thus identifying targets whose processing or degradation may be the basis for RNase E essentiality. Remarkably prominent in this group were mRNAs implicated in energy-generating pathways or in the synthesis or degradation of macromolecules.
Mol Microbiol 2002 Mar
PMID:RNase G complementation of rne null mutation identifies functional interrelationships with RNase E in Escherichia coli. 1195 97

Bacteriophage P4 immunity is controlled by a small stable RNA (CI RNA) that derives from the processing of primary transcripts. In previous works, we observed that the endonuclease RNase P is required for the maturation of CI RNA 5'-end; moreover, we found that polynucleotide phosphorylase (PNPase), a 3' to 5' RNA-degrading enzyme, is required for efficient 5'-end processing of CI RNA, suggesting that 3'-end degradation of the primary transcript might be involved in the production of proper RNase P substrates. Here, we demonstrate that another Escherichia coli nuclease, RNase E, would appear to be involved in this process. We found that transcripts of the P4 immunity region are modified by the post-transcriptional addition of short poly(A) tails and heteropolymeric tails with prevalence of A residues. Most oligoadenylated transcripts encompass the whole cI locus and are thus compatible as intermediates in the CI RNA maturation pathway. On the contrary, in a polynucleotide phosphorylase (PNPase)-defective host, adenylation occurred most frequently within cI, implying that such transcripts are targeted for degradation. We did not find polyadenylation in a pcnB mutant, suggesting that the pcnB-encoded polyadenyl polymerase I (PAP I) is the only enzyme responsible for modification of P4 immunity transcripts. Maturation of CI RNA 5'-end in such a mutant was impaired, further supporting the idea that processing of the 3'-end of primary transcripts is an important step for efficient maturation of CI RNA by RNase P.
J Mol Biol 2002 Apr 26
PMID:RNase E and polyadenyl polymerase I are involved in maturation of CI RNA, the P4 phage immunity factor. 1205 40

Cleavage by RNase E is believed to be the rate-limiting step in the degradation of many RNAs. These cleavages are modulated by 5' end-phosphorylation, folding and translation of the mRNA in question. Here, we present data suggesting that these cleavages are also regulated by environmental conditions. We report that rpsO mRNA, 15 minutes after a shift to 44 degrees C, is stabilized in cells grown in minimal medium. This stabilization is correlated with a reduction in the efficiency of the RNase E cleavage which initiates its decay. We also observe the appearance of RNA fragments previously detected following RNase E inactivation and a defect in the adaptation of RNase E concentration. These observations, coupled to the fact that RNase E overproduction slightly reduces the accumulation of the rpsO mRNA, suggest that this stabilization is caused in part by a limitation in RNase E concentration. An increase in the steady-state level of rpsT mRNA is also observed following a shift to 44 degrees C in minimal medium; however, processing of the 9 S rRNA precursor is not affected under these conditions. We thus propose that RNase E concentration changes in the cell in response to environmental conditions and that these changes can selectively affect the processing and the stability of individual mRNAs. Our data also indicate that the efficiency of cleavage of the rpsO mRNA by RNase E is modified by other factor(s) which remain to be identified.
J Mol Biol 2002 May 31
PMID:Both temperature and medium composition regulate RNase E processing efficiency of the rpsO mRNA coding for ribosomal protein S15 of Escherichia coli. 1205 11


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