sigma 70 Is the Principal Sigma Factor Responsible for Transcription of acs, Which Encodes Acetyl Coenzyme A Synthetase in Escherichia coli (original) (raw)
Related papers
1995
Updated information and services can be found at: These include: CONTENT ALERTS more» cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new articles http://journals.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders: http://journals.asm.org/site/subscriptions/ To subscribe to to another ASM Journal go to: on October 17, 2013 by guest Acetyl coenzyme A synthetase (Acs) activates acetate to acetyl coenzyme A through an acetyladenylate intermediate; two other enzymes, acetate kinase (Ack) and phosphotransacetylase (Pta), activate acetate through an acetyl phosphate intermediate. We subcloned acs, the Escherichia coli open reading frame purported to encode Acs (F. R. Blattner, V. Burland, G. Plunkett III, H. J. Sofia, and D. L. Daniels, Nucleic Acids Res. 21:5408-5417, 1993)
Regulation of the Acetoin Catabolic Pathway Is Controlled by Sigma L in Bacillus subtilis
Journal of Bacteriology, 2001
Bacillus subtilis grown in media containing amino acids or glucose secretes acetate, pyruvate, and large quantities of acetoin into the growth medium. Acetoin can be reused by the bacteria during stationary phase when other carbon sources have been depleted. The acoABCL operon encodes the E1␣, E1, E2, and E3 subunits of the acetoin dehydrogenase complex in B. subtilis. Expression of this operon is induced by acetoin and repressed by glucose in the growth medium. The acoR gene is located downstream from the acoABCL operon and encodes a positive regulator which stimulates the transcription of the operon. The product of acoR has similarities to transcriptional activators of sigma 54-dependent promoters. The four genes of the operon are transcribed from a ؊12, ؊24 promoter, and transcription is abolished in acoR and sigL mutants. Deletion analysis showed that DNA sequences more than 85 bp upstream from the transcriptional start site are necessary for full induction of the operon. These upstream activating sequences are probably the targets of AcoR. Analysis of an acoR-lacZ strain of B. subtilis showed that the expression of acoR is not induced by acetoin and is repressed by the presence of glucose in the growth medium. Transcription of acoR is also negatively controlled by CcpA, a global regulator of carbon catabolite repression. A specific interaction of CcpA in the upstream region of acoR was demonstrated by DNase I footprinting experiments, suggesting that repression of transcription of acoR is mediated by the binding of CcpA to the promoter region of acoR.
Regulation of Acetyl Coenzyme A Synthetase in Escherichia coli
Journal of Bacteriology, 2000
Updated information and services can be found at: These include: REFERENCES http://jb.asm.org/content/182/15/4173#ref-list-1 at: This article cites 45 articles, 26 of which can be accessed free CONTENT ALERTS more» articles cite this article), Receive: RSS Feeds, eTOCs, free email alerts (when new http://journals.asm.org/site/misc/reprints.xhtml Information about commercial reprint orders: http://journals.asm.org/site/subscriptions/ To subscribe to to another ASM Journal go to:
Expression of Two Escherichia coli Acetyl-CoA Carboxylase Subunits Is Autoregulated
Journal of Biological Chemistry, 2003
Acetyl-CoA carboxylase (ACC) catalyzes the first step of fatty acid biosynthesis, the synthesis of malonyl-CoA from acetyl-CoA using ATP and bicarbonate. In Escherichia coli and most other bacteria, ACC is composed of four subunits encoded by accA, accB, accC, and accD. Prior work from this laboratory showed that the in vivo expression of the accBC operon had a strikingly nonlinear response to gene copy number (Li, S.-J, and Cronan, J. E., Jr. (1993) J. Bacteriol. 175, 332-340) in that the presence of 50 or more copies of the accBC operon resulted in only a 2-3-fold increase in AccB and AccC. We now report that AccB functions to negatively regulate transcription of the accBC operon. Expression of a chimeric protein consisting of the N terminus of E. coli AccB and the C-terminal bioinylation domain of Bacillus subtilis AccB down-regulated transcription of the E. coli accBC operon. A truncated form of AccB consisting of the N-terminal 68 amino acids of E. coli AccB was sufficient to negatively regulate the accBC operon. In vivo bypass of acetyl-CoA carboxylase activity by expression of a malonyl-CoA synthase from Rhizobium trifolii allowed construction of strain deleted for the accA and accB genes. Unexpectedly, the ⌬accB mutation could not be resolved from the ⌬accA mutation. Transcription of the accBC operon in the ⌬accB ⌬accA strain continued well into stationary phase under growth conditions that normally result in greatly decreased transcription. These data support a model in which AccB acts as an autoregulator of accBC operon transcription.
The Bacterial Enhancer-Dependent sigma 54 (sigma N) Transcription Factor
Journal of Bacteriology, 2000
The initiation of transcription is a complex process involving many different steps. These steps are all potential control points for regulating gene expression, and many have been exploited by bacteria to give rise to sophisticated regulatory mechanisms that allow the cell to adapt to changing growth regimens. Before they can transcribe from specific DNA promoter sequences, bacterial core RNA polymerases (with subunit composition ␣ 2 Ј) must combine with a dissociable sigma subunit () to form RNA polymerase holoenzyme (␣ 2 Ј). Since the discovery of factors , it has become clear that these proteins are central to the function of the RNA polymerase holoenzyme. The reversible binding of alternative factors allows formation of different holoenzymes able to distinguish groups of promoters required for different cellular functions. In addition to double-strand DNA promoter recognition and binding, proteins are closely involved in promoter melting (e.g., references 31, 36, 49, 51, 74, 76, 128), inhibit nonspecific initiation, are targets for activators, and control early transcription through promoter clearance and release from RNA polymerase . Here we describe the functioning of the bacterial 54 -RNA polymerase that is the target for sophisticated signal transduction pathways (103) involving activation via remote enhancer elements (5, 95).
Salmonella enterica serovar Typhimurium (S. Typhimurium) elicits the starvation-stress response (SSR) dueto starvation for an essential nutrient, e.g. a carbon/energy source (C-source). As part of the SSR, the alternative sigma factor sigma^E is activated and induced. The authors suspect that this activation is, in part, triggered by changes in the S. Typhimurium cell envelope occurring during the adaptation from growth to carbon/energy starvation (C-starvation), and resulting in an increased need for sE-regulated factors involved in the proper folding and assembly of newly synthesized proteins destined for this extracytoplasmic compartment. This led to the hypothesis that a sE activation signal might arise during C-source shifts that cause the induction of proteins localized to the extracytoplasmic compartment, i.e. the outer membrane or periplasm, of the cell. To test this hypothesis, cultures were grown in minimal medium containing enough glucose t or each mid-exponential-phase,plus a non-limiting amount of a secondary ‘less-preferred’ but utilizable carbon/energy source. The sigma^E activity was then monitored using plasmids carrying rpoEP1– and rpoEP2–lacZ transcriptional fusions, which exhibit sigma^E-independent and -dependent lacZ expression, respectively. The secondary C-sources maltose, succinate and citrate, which have extracytoplasmic components involved in their utilization (e.g. LamB), resulted in a discernible diauxic lag period and a sustained increase in sigma^E activity. Growth transition from glucose to other utilizable phosphotransferase (PTS) and non-PTS C-sources, such as trehalose, mannose, mannitol, fructose, glycerol, D-galactose or L-arabinose, did not cause a discernible diauxic lag period or a sustained increase in sE activity. Interestingly, a shift from glucose to melibiose, which does not use an extracytoplasmic-localized protein for uptake, did cause an observable diauxic lag period but did not result in a sustained increase in sigma^E activity. In addition, overexpression of LamB from an arabinose-inducible promoter leads to a significant increase in sigma^E activity in the absence of a glucose to maltose shift or C-starvation. Furthermore, a (del)lamB::omega-Km^r mutant, lacking the LamB maltoporin, exhibited an approximately twofold reduction in the sustained sigma^E activity observed during a glucose to maltose shift, again supporting the hypothesis. Interestingly, the LamB protein lacks the typical Y-X-F terminal tripeptide of the OmpC-like peptides that activate DegS protease activity leading to sigma^E activation. It does, however, possess a terminal pentapeptide (Q-M-E-I-W-W)that may function as a ligand for a putative class II PDZ-binding site. The authors therefore propose that the sigma^E regulon of S. Typhimurium not only is induced in response to deleterious environmental conditions, but also plays a role in the adaptation of cells to new growth conditions that necessitate changes in the extracytoplasmic compartment of the cell, which may involve alternative signal recognition and activation pathways that are independent of DegS.
Negative regulation of σ70-driven promoters by σ70
Research in Microbiology, 2011
The Escherichia coli yjbEFGH operon, encoding genes involved in exopolysaccharide production, has previously been shown to be induced by osmotic stress and to be negatively regulated by s 38 . Promoter analysis suggested that like most E. coli genes, its transcription is driven by the housekeeping sigma factor s 70 . Indeed, manipulation of any of the other five alternative sigma factors did not affect its induction by osmotic stress. Surprisingly, when assayed in a strain expressing low levels of s 70 , yjbEFGH induction in response to osmotic stress was higher than in a strain expressing normal levels of s 70 . Similar phenomena were observed in the s 70 -driven promoters of sulA, uvrA, recA, fecI, entC and lacZ, the transcription of which is directly controlled by a repressor protein (LexA, Fur and LacI), but not in promoters of the housekeeping genes ftsA and ftsY, or in s 38 -driven treA promoter. Since transcription factors are generally present in the cell in low numbers, we hypothesize that a decrease in s 70 , that drives the expression of lexA, fur and lacI as well, further diminishes their number in the cell and thus de-represses the induction of genes which are subjected to their repression.
Anti-Sigma Factors in E. coli: Common Regulatory Mechanisms Controlling Sigma Factors Availability
2013
In bacteria, transcriptional regulation is a key step in cellular gene expression. All bacteria contain a core RNA polymerase that is catalytically competent but requires an additional σ factor for specific promoter recognition and correct transcriptional initiation. The RNAP core is not able to selectively bind to a given σ factor. In contrast, different σ factors have different affinities for the RNAP core. As a consequence, the concentration of alternate σ factors requires strict regulation in order to properly control the delicate interplay among them, which favors the competence for the RNAP core. This control is archived by different σ/anti-σ controlling mechanisms that shape complex regulatory networks and cascades, and enable the response to sudden environmental cues, whose global understanding is a current challenge for systems biology. Although there have been a number of excellent studies on each of these σ/anti-σ post-transcriptional regulatory systems, no comprehensive comparison of these mechanisms in a single model organism has been conducted. Here, we survey all these systems in E. coli dissecting and analyzing their inner workings and highlightin their differences. Then, following an integral approach, we identify their commonalities and outline some of the principles exploited by the cell to effectively and globally reprogram the transcriptional machinery. These principles provide guidelines for developing biological synthetic circuits enabling an efficient and robust response to sudden stimuli.
Protein Expression and Purification
shown directly to be a s factor based on biochemical This paper reports the overproduction and the de-studies. It binds to and confers promoter specificity on tails of a rapid method to purify active s S monomers core RNA polymerase (4,9). from a T7 RNA polymerase-based protein expression Any detailed studies of the structure and functions system. This 2-day procedure involves solubilizing inof a particular protein require that the protein be availclusion bodies in sarkosyl detergent, removal of sarkoable in reasonable amounts. We present in this report syl by dialysis, and a single gel filtration column chrothe details of a rapid procedure for obtaining pure and matography step. The final yield of s S is about 9 mg of active monomeric s S in large quantities for physical approximately 92% purity from 0.5 g of wet weight and biochemical characterizations. cells. Overproduced s S binds to core RNA polymerase and supports transcription from the bolAp1 promoter, MATERIAL AND METHODS a s S-dependent promoter.
PLOS Genetics, 2011
Two highly similar RNA polymerase sigma subunits, s F and s G , govern the early and late phases of forespore-specific gene expression during spore differentiation in Bacillus subtilis. s F drives synthesis of s G but the latter only becomes active once engulfment of the forespore by the mother cell is completed, its levels rising quickly due to a positive feedback loop. The mechanisms that prevent premature or ectopic activation of s G while discriminating between s F and s G in the forespore are not fully comprehended. Here, we report that the substitution of an asparagine by a glutamic acid at position 45 of s G (N45E) strongly reduced binding by a previously characterized anti-sigma factor, CsfB (also known as Gin), in vitro, and increased the activity of s G in vivo. The N45E mutation caused the appearance of a sub-population of pre-divisional cells with strong activity of s G . CsfB is normally produced in the forespore, under s F control, but sigGN45E mutant cells also expressed csfB and did so in a s G -dependent manner, autonomously from s F . Thus, a negative feedback loop involving CsfB counteracts the positive feedback loop resulting from ectopic s G activity. N45 is invariant in the homologous position of s G orthologues, whereas its functional equivalent in s F proteins, E39, is highly conserved. While CsfB does not bind to wildtype s F , a E39N substitution in s F resulted in efficient binding of CsfB to s F . Moreover, under certain conditions, the E39N alteration strongly restrains the activity of s F in vivo, in a csfB-dependent manner, and the efficiency of sporulation. Therefore, a single amino residue, N45/E39, is sufficient for the ability of CsfB to discriminate between the two foresporespecific sigma factors in B. subtilis.