Effect of variation of charged and uncharged tRNA(Trp) levels on ppGpp synthesis in Escherichia coli

Rojiani, Mumtaz V.; Jakubowski, Hieronim; Goldman, Emanuel

doi:10.1128/jb.171.12.6493-6502.1989

Cited by 36 publications

(36 citation statements)

References 32 publications

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“…The only known mechanism by which the relA pathway of ppGpp synthesis is induced in vivo is the activation of the RelA protein by the binding of uncharged tRNA in the acceptor sites of translating ribosomes (13,50). Thus, it can be inferred that glucose deprivation in Vibrio sp.…”

Section: Materuils and Methodsmentioning

confidence: 99%

Stringent control during carbon starvation of marine Vibrio sp. strain S14: molecular cloning, nucleotide sequence, and deletion of the relA gene

et al. 1994

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In order to evaluate the role of the stringent response in starvation adaptations of the marine Vtbrio sp. strain S14, we have cloned the relA gene and generated relaxed mutants of this organism. The concentrations of biologically available nutrients are generally low in natural bacterial habitats (34, 35), and adaptations to restrictions in nutrient and energy availability may contribute significantly to the fitness of bacteria in such environments. Marine vibrios are adequate models for studies of starvation responses, and their adaptations include the development of general stress resistance and the ability to survive extended periods of complete carbon and energy starvation. Alterations in cell surface components, adhesive properties, nutrient scavenging, and uptake systems are commonly observed (reviewed in references 21, 22, and 33). The marine isolate Vibrio sp. strain S14 has served as a model organism in many of these studies (38). It responds to multiplenutrient starvation by a developmental process comprising the temporally ordered induction of more than 66 starvationinduced (Sti) proteins (39). The identities of the Sti proteins are, with some exceptions (17), unknown, but it is assumed that phenotypic adaptations during the starvation response can be ascribed to the induction of specific Sti proteins. That is the case with Escherichia coli, in which several of the phenotypes that are expressed during stationary phase are dependent on specific members of the as or RpoS regulon (14).The transition of growing Vbrio sp. strain S14 cells to multiple-nutrient starvation includes the induction of the stringent response (39), a regulatory network with pleiotropic effects on cellular physiology, primarily studied as it occurs in E. coli (3). Evidence for a role of the stringent response in the starvation adaptation of Vibrio sp. strain S14 was obtained

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Section: Materuils and Methodsmentioning

confidence: 99%

Stringent control during carbon starvation of marine Vibrio sp. strain S14: molecular cloning, nucleotide sequence, and deletion of the relA gene

et al. 1994

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“…Levels of ppGpp were assayed as previously described (52). Saturated E. coli cultures were first pelleted and washed two times in prewarmed Mops dropout medium and then were used to inoculate assay cultures.…”

Section: Methodsmentioning

confidence: 99%

Translation quality control is critical for bacterial responses to amino acid stress

Bullwinkle

Ibba

2016

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

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Gene expression relies on quality control for accurate transmission of genetic information. One mechanism that prevents amino acid misincorporation errors during translation is editing of misacylated tRNAs by aminoacyl-tRNA synthetases. In the absence of editing, growth is limited upon exposure to excess noncognate amino acid substrates and other stresses, but whether these physiological effects result solely from mistranslation remains unclear. To explore if translation quality control influences cellular processes other than protein synthesis, an Escherichia coli strain defective in Tyr-tRNA Phe editing was used. In the absence of editing, cellular levels of aminoacylated tRNA Phe were elevated during amino acid stress, whereas in the wild-type strain these levels declined under the same growth conditions. In the editing-defective strain, increased levels of aminoacylated tRNA Phe led to continued synthesis of the PheL leader peptide and attenuation of pheA transcription under amino acid stress. Consequently, in the absence of editing, activation of the phenylalanine biosynthetic operon becomes less responsive to phenylalanine limitation. In addition to raising aminoacylated tRNA levels, the absence of editing lowered the amount of deacylated tRNA Phe in the cell. This reduction in deacylated tRNA was accompanied by decreased synthesis of the second messenger guanosine tetraphosphate and limited induction of stringent response-dependent gene expression in editing-defective cells during amino acid stress. These data show that a single qualitycontrol mechanism, the editing of misacylated aminoacyl-tRNAs, provides a critical checkpoint both for maintaining the accuracy of translation and for determining the sensitivity of transcriptional responses to amino acid stress.translation | quality control | stress | stringent response

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Section: Introductionmentioning

confidence: 99%

“…The relA locus encodes ppGpp synthetase 1 (17). The relA system monitors the ratio of charged and uncharged tRNA at the ribosome, and upon amino acid starvation is responsible for the synthesis of -1000 pmol of ppGpp per ml per OD60 unit of cells (17)(18)(19)(20).In the absence of a functional relA locus, basal ppGpp levels (<100 pmolOD-ayml-') still vary inversely with the growth rate, implying that there is a second ppGpp-synthesizing system (ppGpp synthetase II; refs. 17 and 18).…”

mentioning

confidence: 99%

Guanosine 3'-diphosphate 5'-diphosphate is not required for growth rate-dependent control of rRNA synthesis in Escherichia coli.

Gaál

Gourse

1990

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

109

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ABSTRACTrRNA synthesis in Escherichia coli is subject to at least two regulation systems, growth rate-dependent control and stringent control. The inverse correlation between rRNA synthesis rates and guanosine 3'-diphosphate 5'-diphosphate (ppGpp) levels under various physiological conditions has led to the supposition that ppGpp is the mediator of both control mechanisms by inhibiting transcription from rrn PI promoters. Recently, reL4 spoT-strains have been constructed in which both ppGpp synthesis pathways most likely have been removed (M. Cashel, personal communication). We have confirmed that such strains produce no detectable ppGpp and therefore offer a direct means for testing the involvement of ppGpp in the regulation of rRNA synthesis in vivo. Stringent control was determined by measurement of rRNA synthesis after amino acid starvation, while growth rate control was determined by measurement of rRNA synthesis under different nutritional conditions. As expected, the reL4-spoT-strain is relaxed for stringent control. However, growth rate-dependent regulation is unimpaired. These results indicate that growth rate regulation can occur in the absence of ppGpp and imply that ppGpp is not the mediator, or at least is not the sole mediator, of growth rate-dependent control. Therefore, growth rate-dependent control and stringent control may utilize different mechanisms for regulating stable RNA synthesis. rRNA synthesis constitutes a major fraction of the RNA synthesis in Escherichia coli. In cells growing under steadystate conditions, rRNA and tRNA synthesis rates are proportional to the square of the growth rate in order to meet the cell's requirements for protein synthesis, a phenomenon termed growth rate-dependent control (1-3). rRNA transcription is also subject to stringent control, a response to aminoacyl-tRNA limitation that results in severe inhibition of stable RNA (rRNA and tRNA) synthesis. rRNA synthesis is regulated primarily at the level of transcription initiation at the PI promoters of the seven rRNA operons (4-8). A negative feedback system responsive to the level of translationally competent ribosomes has been shown to control transcription from rrn PI and tRNA promoters (9-13) and has been proposed to be the mechanism for growth rate-dependent control (2, 7, 9).The role of the relA locus in the control of ribosome synthesis is a longstanding question in bacterial physiology (14). A rapid decline in stable RNA synthesis after amino acid starvation in relA' but not in relA-cells coincides with a large increase in the concentration of guanosine 3'-diphosphate 5'-diphosphate ("guanosine tetraphosphate," ppGpp; see refs. 15 and 16). The relA locus encodes ppGpp synthetase 1 (17). The relA system monitors the ratio of charged and uncharged tRNA at the ribosome, and upon amino acid starvation is responsible for the synthesis of -1000 pmol of ppGpp per ml per OD60 unit of cells (17)(18)(19)(20).In the absence of a functional relA locus, basal ppGpp levels (<100 pmolOD-ayml-') still vary inversely with...

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Effect of variation of charged and uncharged tRNA(Trp) levels on ppGpp synthesis in Escherichia coli

Cited by 36 publications

References 32 publications

Stringent control during carbon starvation of marine Vibrio sp. strain S14: molecular cloning, nucleotide sequence, and deletion of the relA gene

Stringent control during carbon starvation of marine Vibrio sp. strain S14: molecular cloning, nucleotide sequence, and deletion of the relA gene

Translation quality control is critical for bacterial responses to amino acid stress

Guanosine 3'-diphosphate 5'-diphosphate is not required for growth rate-dependent control of rRNA synthesis in Escherichia coli.

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