scholarly journals Role of Integration Host Factor in the Transcriptional Activation of Flagellar Gene Expression in Caulobacter crescentus

2005 ◽  
Vol 187 (3) ◽  
pp. 949-960 ◽  
Author(s):  
Rachel E. Muir ◽  
James W. Gober
Keyword(s):  
Gene Expression ◽  
Caulobacter Crescentus ◽  
Consensus Sequence ◽  
Integration Host Factor ◽  
Host Factor ◽  
Flagellar Gene ◽  
Class Iii ◽  
Mild Defect ◽  
Flagellar Genes ◽  
Class Iv

ABSTRACT In the Caulobacter crescentus predivisional cell, class III and IV flagellar genes, encoding the extracytoplasmic components of the flagellum, are transcribed in the nascent swarmer compartment. This asymmetric expression pattern is attributable to the compartmentalized activity of the σ54-dependent transcriptional activator FlbD. Additionally, these temporally transcribed flagellar promoters possess a consensus sequence for the DNA-binding protein integration host factor (IHF), located between the upstream FlbD binding site and the promoter sequences. Here, we deleted the C. crescentus gene encoding the β-subunit of the IHF, ihfB (himD), and examined the effect on flagellar gene expression. The ΔihfB strain exhibited a mild defect in cell morphology and impaired motility. Using flagellar promoter reporter fusions, we observed that expression levels of a subset of class III flagellar promoters were decreased by the loss of IHF. However, one of these promoters, fliK-lacZ, exhibited a wild-type cell cycle-regulated pattern of expression in the absence of IHF. Thus, IHF is required for maximal transcription of several late flagellar genes. The ΔihfB strain was found to express significantly reduced amounts of the class IV flagellin, FljL, as a consequence of reduced transcriptional activity. Our results indicate that the motility defect exhibited by the ΔihfB strain is most likely attributable to its failure to accumulate the class IV-encoded 27-kDa flagellin subunit, FljL.

scholarly journals A Membrane-Associated Protein, FliX, Is Required for an Early Step in Caulobacter Flagellar Assembly

1998 ◽  
Vol 180 (8) ◽  
pp. 2175-2185 ◽  
Author(s):  
Christian D. Mohr ◽  
Joanna K. MacKichan ◽  
Lucy Shapiro
Keyword(s):  
Cell Cycle ◽  
Caulobacter Crescentus ◽  
Signal Sequence ◽  
Early Stage ◽  
Class Ii ◽  
Flagellar Gene ◽  
Class Iii ◽  
Isolation And Characterization ◽  
Flagellar Assembly ◽  
Flagellar Genes

ABSTRACT The ordered assembly of the Caulobacter crescentusflagellum is accomplished in part through the organization of the flagellar structural genes in a regulatory hierarachy of four classes. Class II genes are the earliest to be expressed and are activated at a specific time in the cell cycle by the CtrA response regulator. In order to identify gene products required for early events in flagellar assembly, we used the known phenotypes of class II mutants to identify new class II flagellar genes. In this report we describe the isolation and characterization of a flagellar gene, fliX. AfliX null mutant is nonmotile, lacks a flagellum, and exhibits a marked cell division defect. Epistasis experiments placedfliX within class II of the flagellar regulatory hierarchy, suggesting that FliX functions at an early stage in flagellar assembly. The fliX gene encodes a 15-kDa protein with a putative N-terminal signal sequence. Expression of fliX is under cell cycle control, with transcription beginning relatively early in the cell cycle and peaking in Caulobacter predivisional cells. Full expression of fliX was found to be dependent onctrA, and DNase I footprinting analysis demonstrated a direct interaction between CtrA and the fliX promoter. ThefliX gene is located upstream and is divergently transcribed from the class III flagellar gene flgI, which encodes the basal body P-ring monomer. Analysis of thefliX-flgI intergenic region revealed an arrangement ofcis-acting elements similar to that of another set ofCaulobacter class II and class III flagellar genes,fliL-flgF, that is also divergently transcribed. In parallel with the FliL protein, FliX copurifies with the membrane fraction, and although its expression is cell cycle controlled, the protein is present throughout the cell cycle.

scholarly journals Themes and Variations: Regulation of RpoN-Dependent Flagellar Genes across Diverse Bacterial Species

Scientifica ◽  
2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Jennifer Tsang ◽  
Timothy R. Hoover
Keyword(s):  
Gene Expression ◽  
Campylobacter Jejuni ◽  
Sigma Factor ◽  
Caulobacter Crescentus ◽  
Bacterial Species ◽  
Alternative Sigma Factor ◽  
Flagellar Gene ◽  
Complex Process ◽  
Flagellar Biogenesis ◽  
Flagellar Genes

Flagellar biogenesis in bacteria is a complex process in which the transcription of dozens of structural and regulatory genes is coordinated with the assembly of the flagellum. Although the overall process of flagellar biogenesis is conserved among bacteria, the mechanisms used to regulate flagellar gene expression vary greatly among different bacterial species. Many bacteria use the alternative sigma factorσ54(also known as RpoN) to transcribe specific sets of flagellar genes. These bacteria include members of the Epsilonproteobacteria (e.g.,Helicobacter pyloriandCampylobacter jejuni), Gammaproteobacteria (e.g.,VibrioandPseudomonasspecies), and Alphaproteobacteria (e.g.,Caulobacter crescentus). This review characterizes the flagellar transcriptional hierarchies in these bacteria and examines what is known about how flagellar gene regulation is linked with other processes including growth phase, quorum sensing, and host colonization.

scholarly journals Integration Host Factor Positively Regulates Virulence Gene Expression in Vibrio cholerae

2008 ◽  
Vol 190 (13) ◽  
pp. 4736-4748 ◽  
Author(s):  
Emily Stonehouse ◽  
Gabriela Kovacikova ◽  
Ronald K. Taylor ◽  
Karen Skorupski
Keyword(s):  
Gene Expression ◽  
Vibrio Cholerae ◽  
Virulence Gene ◽  
Toxin Production ◽  
Dnase I ◽  
Integration Host Factor ◽  
Host Factor ◽  
Mobility Shift ◽  
Virulence Gene Expression ◽  
Dnase I Footprinting

ABSTRACT Virulence gene expression in Vibrio cholerae is dependent upon a complex transcriptional cascade that is influenced by both specific and global regulators in response to environmental stimuli. Here, we report that the global regulator integration host factor (IHF) positively affects virulence gene expression in V. cholerae. Inactivation of ihfA and ihfB, the genes encoding the IHF subunits, decreased the expression levels of the two main virulence factors tcpA and ctx and prevented toxin-coregulated pilus and cholera toxin production. IHF was found to directly bind to and bend the tcpA promoter region at an IHF consensus site centered at position −162 by using gel mobility shift assays and DNase I footprinting experiments. Deletion or mutation of the tcpA IHF consensus site resulted in the loss of IHF binding and additionally disrupted the binding of the repressor H-NS. DNase I footprinting revealed that H-NS protection overlaps with both the IHF and the ToxT binding sites at the tcpA promoter. In addition, disruption of ihfA in an hns or toxT mutant background had no effect on tcpA expression. These results suggest that IHF may function at the tcpA promoter to alleviate H-NS repression.

scholarly journals A Dual Binding Site for Integration Host Factor and the Response Regulator CtrA inside the Caulobacter crescentus Replication Origin

2003 ◽  
Vol 185 (18) ◽  
pp. 5563-5572 ◽  
Author(s):  
Rania Siam ◽  
Ann Karen C. Brassinga ◽  
Gregory T. Marczynski
Keyword(s):  
Binding Site ◽  
Replication Origin ◽  
Protein Concentration ◽  
Caulobacter Crescentus ◽  
Response Regulator ◽  
Chromosome Replication ◽  
Integration Host Factor ◽  
Host Factor ◽  
Dna Mutations ◽  
Ihf Protein

ABSTRACT The response regulator CtrA controls chromosome replication by binding to five sites, a, b, c, d, and e, inside the Caulobacter crescentus replication origin (Cori). In this study, we demonstrate that integration host factor (IHF) binds Cori over the central CtrA binding site c. Surprisingly, IHF and CtrA share DNA recognition sequences. Rather than promoting cooperative binding, IHF binding hinders CtrA binding to site c and nearby site d. Unlike other CtrA binding sites, DNA mutations in the CtrA c/IHF site uniquely impair autonomous Cori plasmid replication. These mutations also alter transcription from distant promoters more than 100 bp away. When the CtrA c/IHF site was deleted from the chromosome, these cells grew slowly and became selectively intolerant to a CtrA phosphor-mimic allele (D51E). Since CtrA protein concentration decreases during the cell cycle as IHF protein concentration increases, we propose a model in which IHF displaces CtrA in order to bend Cori and promote efficient chromosome replication.

scholarly journals Clofazimine targets essential nucleoid associated protein, mycobacterial integration host factor (mIHF), inMycobacterium tuberculosis

2017 ◽  
Author(s):  
Wanliang Shi ◽  
Shuo Zhang ◽  
Jie Feng ◽  
Peng Cui ◽  
Wenhong Zhang ◽  
...  
Keyword(s):  
Gene Expression ◽  
Integration Host Factor ◽  
Host Factor ◽  
Chromosome Organization ◽  
Dna Protection ◽  
Recent Interest ◽  
Phenazine Derivative ◽  
Global Gene Regulation ◽  
Mdr Tb ◽  
Unique Ability

Clofazimine (CFZ) is a phenazine derivative used for treatment of leprosy, MDR-TB and XDR-TB. There is recent interest in understanding how CFZ works following the demonstration of its unique ability to shorten the treatment of MDR-TB. However, the target of CFZ in mycobacteria has remained elusive. Here, we show that CFZ binds to mycobacterial integration host factor (mIHF), which is an essential nucleoid associated protein in mycobacteria involved in DNA protection, chromosome organization and global gene regulation. We demonstrate that CFZ inhibits mIHF binding to DNA and interferes with mycobacterial gene expression. This mode of action is unique among all antibiotics including antimycibacterial agents and may help to explain its unusual action againstMycobacterium tuberculosis. Our study provides new insight about the mechanism of action of this intriguing drug and has implications for developing more effective treatment of TB.

scholarly journals VisN and VisR Are Global Regulators of Chemotaxis, Flagellar, and Motility Genes in Sinorhizobium (Rhizobium) meliloti

2000 ◽  
Vol 182 (3) ◽  
pp. 782-788 ◽  
Author(s):  
Victor Sourjik ◽  
Paul Muschler ◽  
Birgit Scharf ◽  
Rüdiger Schmitt
Keyword(s):  
Gene Expression ◽  
Rhizobium Meliloti ◽  
Class Ii ◽  
Functional Class ◽  
Class I ◽  
Class Iii ◽  
Transcription Activator ◽  
Western Blots ◽  
Class Iib ◽  
Flagellar Genes

ABSTRACT The known 41 flagellar, chemotaxis, and motility genes ofSinorhizobium (Rhizobium) meliloti contained in the “flagellar regulon” are organized as seven operons and six transcription units that map to a contiguous 45-kb chromosomal region. By probing gene expression on Western blots and with lacZfusions, we have identified two master regulatory genes,visN and visR, contained in one operon. The gene products probably form a heterodimer, VisNR, acting as a global transcription activator of other flagellar genes. The related 27-kDa VisN and VisR proteins are LuxR-type proteins with typical ligand- and DNA-binding domains. The vis operon itself is constitutively transcribed; however, to activate flagellar genes, VisNR seemingly requires the binding of a yet-unknown effector. Gene expression in tester strains with known deficiencies revealed a hierarchy of three classes of flagellar genes: class I comprisesvisN and visR; class II, controlled by VisNR, comprises flagellar assembly (class IIA) and motor (class IIB) genes; and class III comprises flagellin and chemotaxis genes that require functional class I and class IIA genes for expression. In contrast to their enterobacterial counterparts, mot genes belong to class II without exerting control over class III genes. While the general hierarchy of gene expression resembles the enterobacterial scheme, the assignment of mot genes to class IIB and the global control by a LuxR-type VisNR activator are new features distinguishing the S. meliloti flagellar gene system.

scholarly journals A Bacterial Signal Transduction System Controls Genetic Exchange and Motility

2002 ◽  
Vol 184 (4) ◽  
pp. 913-918 ◽  
Author(s):  
Andrew S. Lang ◽  
J. Thomas Beatty
Keyword(s):  
Signal Transduction ◽  
Rhodobacter Capsulatus ◽  
Class Ii ◽  
Genetic Exchange ◽  
Natural Environments ◽  
Flagellar Gene ◽  
Class Iii ◽  
Signal Transduction System ◽  
Gene Transcripts ◽  
Flagellar Genes

ABSTRACT The bacterium Rhodobacter capsulatus is capable of an unusual form of genetic exchange, mediated by a transducing bacteriophage-like particle called the gene transfer agent (GTA). GTA production by R. capsulatus is controlled at the level of transcription by a cellular two-component signal transduction system that includes a putative histidine kinase (CckA) and response regulator (CtrA). We found that, in addition to regulating genetic exchange by R. capsulatus, this signal transduction system controls motility. As with the regulation of GTA production, the control of motility by CckA and CtrA occurs through modulation of gene transcription. Disruptions of the cckA and ctrA genes resulted in a loss of class II, class III, and class IV flagellar gene transcripts, suggesting that cckA and ctrA function in motility as class I flagellar genes. We also found that, analogous to the GTA genes, transcription of R. capsulatus flagellar genes appears to be growth phase dependent: class II flagellar gene transcripts are maximal in the mid-log phase of the culture growth cycle, whereas class III gene transcripts are maximal in the late-log phase of growth. We speculate that coordinate regulation of motility and GTA-mediated genetic exchange in R. capsulatus exists because these two processes are complementary mechanisms for cells to cope with unfavorable conditions in natural environments.

Transcriptional regulation of the uptake [NiFe]hydrogenase genes in Rhodobacter capsulatus

2005 ◽  
Vol 33 (1) ◽  
pp. 28-32 ◽  
Author(s):  
P.M. Vignais ◽  
S. Elsen ◽  
A. Colbeau
Keyword(s):  
Gene Expression ◽  
Rhodobacter Capsulatus ◽  
Response Regulator ◽  
Regulatory System ◽  
Integration Host Factor ◽  
Host Factor ◽  
Promoter Recognition ◽  
The Stability ◽  
A Site

Transcription of the hupSL genes, which encode the uptake [NiFe]hydrogenase of Rhodobacter capsulatus, is specifically activated by H2. Three proteins are involved, namely the H2-sensor HupUV, the histidine kinase HupT and the transcriptional activator HupR. hupT and hupUV mutants have the same phenotype, i.e. an increased level of hupSL expression (assayed by phupS::lacZ fusion) in the absence of H2; they negatively control hupSL gene expression. HupT can autophosphorylate its conserved His217, and in vitro phosphotransfer to Asp54 of its cognate response regulator, HupR, was demonstrated. The non-phosphorylated form of HupR binds to an enhancer site (5′-TTG-N5-CAA) of phupS localized at −162/−152 nt and requires integration host factor to activate fully hupSL transcription. HupUV is an O2-insensitive [NiFe]hydrogenase, which interacts with HupT to regulate the phosphorylation state of HupT in response to H2 availability. The N-terminal domain of HupT, encompassing the PAS domain, is required for interaction with HupUV. This interaction with HupT, leading to the formation of a (HupT)2–(HupUV)2 complex, is weakened in the presence of H2, but incubation of HupUV with H2 has no effect on the stability of the heterodimer/tetramer, HupUV–(HupUV)2, equilibrium. HupSL biosynthesis is also under the control of the global two-component regulatory system RegB/RegA, which controls gene expression in response to redox. RegA binds to a site close to the −35 promoter recognition site and to a site overlapping the integration host factor DNA-binding site (5′-TCACACACCATTG, centred at −87 nt) and acts as a repressor.

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