scholarly journals Regulation of the Single Polar Flagellar Biogenesis

Biomolecules ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 533 ◽  
Author(s):  
Seiji Kojima ◽  
Hiroyuki Terashima ◽  
Michio Homma
Keyword(s):  
Translational Regulation ◽  
Bacterial Species ◽  
Signal Recognition Particle ◽  
Negative Regulator ◽  
Regulation Mechanism ◽  
Guanosine Triphosphate ◽  
Cell Pole ◽  
Flagellar Assembly ◽  
Major Factors ◽  
Flagellar Biogenesis

Some bacterial species, such as the marine bacterium Vibrio alginolyticus, have a single polar flagellum that allows it to swim in liquid environments. Two regulators, FlhF and FlhG, function antagonistically to generate only one flagellum at the cell pole. FlhF, a signal recognition particle (SRP)-type guanosine triphosphate (GTP)ase, works as a positive regulator for flagellar biogenesis and determines the location of flagellar assembly at the pole, whereas FlhG, a MinD-type ATPase, works as a negative regulator that inhibits flagellar formation. FlhF intrinsically localizes at the cell pole, and guanosine triphosphate (GTP) binding to FlhF is critical for its polar localization and flagellation. FlhG also localizes at the cell pole via the polar landmark protein HubP to directly inhibit FlhF function at the cell pole, and this localization depends on ATP binding to FlhG. However, the detailed regulatory mechanisms involved, played by FlhF and FlhG as the major factors, remain largely unknown. This article reviews recent studies that highlight the post-translational regulation mechanism that allows the synthesis of only a single flagellum at the cell pole.

scholarly journals Butanol Tolerance of Lactiplantibacillus plantarum: A Transcriptome Study

Genes ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 181
Author(s):  
Kaloyan Petrov ◽  
Alexander Arsov ◽  
Penka Petrova
Keyword(s):  
Bacterial Species ◽  
Transcriptional Regulators ◽  
Common Species ◽  
Glycerol Metabolism ◽  
Phosphotransferase System ◽  
Promising Alternative ◽  
Butanol Tolerance ◽  
Polysaccharide Biosynthesis ◽  
Major Factors ◽  
Butanol Stress

Biobutanol is a promising alternative fuel with impaired microbial production thanks to its toxicity. Lactiplantibacillus plantarum (L. plantarum) is among the few bacterial species that can naturally tolerate 3% (v/v) butanol. This study aims to identify the genetic factors involved in the butanol stress response of L. plantarum by comparing the differential gene expression in two strains with very different butanol tolerance: the highly resistant Ym1, and the relatively sensitive 8-1. During butanol stress, a total of 319 differentially expressed genes (DEGs) were found in Ym1, and 516 in 8-1. Fifty genes were upregulated and 54 were downregulated in both strains, revealing the common species-specific effects of butanol stress: upregulation of multidrug efflux transporters (SMR, MSF), toxin-antitoxin system, transcriptional regulators (TetR/AcrR, Crp/Fnr, and DeoR/GlpR), Hsp20, and genes involved in polysaccharide biosynthesis. Strong inhibition of the pyrimidine biosynthesis occurred in both strains. However, the strains differed greatly in DEGs responsible for the membrane transport, tryptophan synthesis, glycerol metabolism, tRNAs, and some important transcriptional regulators (Spx, LacI). Uniquely upregulated in the butanol-resistant strain Ym1 were the genes encoding GntR, GroEL, GroES, and foldase PrsA. The phosphoenolpyruvate flux and the phosphotransferase system (PTS) also appear to be major factors in butanol tolerance.

scholarly journals Bacterial Flagellar Filament: A Supramolecular Multifunctional Nanostructure

2021 ◽  
Vol 22 (14) ◽  
pp. 7521
Author(s):  
Marko Nedeljković ◽  
Diego Emiliano Sastre ◽  
Eric John Sundberg
Keyword(s):  
Immune Responses ◽  
Basal Body ◽  
Vaccine Development ◽  
Bacterial Species ◽  
High Variability ◽  
Bacterial Survival ◽  
Bacterial Flagellum ◽  
Capping Proteins ◽  
Flagellar Filament ◽  
Flagellar Assembly

The bacterial flagellum is a complex and dynamic nanomachine that propels bacteria through liquids. It consists of a basal body, a hook, and a long filament. The flagellar filament is composed of thousands of copies of the protein flagellin (FliC) arranged helically and ending with a filament cap composed of an oligomer of the protein FliD. The overall structure of the filament core is preserved across bacterial species, while the outer domains exhibit high variability, and in some cases are even completely absent. Flagellar assembly is a complex and energetically costly process triggered by environmental stimuli and, accordingly, highly regulated on transcriptional, translational and post-translational levels. Apart from its role in locomotion, the filament is critically important in several other aspects of bacterial survival, reproduction and pathogenicity, such as adhesion to surfaces, secretion of virulence factors and formation of biofilms. Additionally, due to its ability to provoke potent immune responses, flagellins have a role as adjuvants in vaccine development. In this review, we summarize the latest knowledge on the structure of flagellins, capping proteins and filaments, as well as their regulation and role during the colonization and infection of the host.

scholarly journals Signal Integration in Quorum Sensing Enables Cross-Species Induction of Virulence in Pectobacterium wasabiae

mBio ◽  
2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Rita S. Valente ◽  
Pol Nadal-Jimenez ◽  
André F. P. Carvalho ◽  
Filipe J. D. Vieira ◽  
Karina B. Xavier
Keyword(s):  
Signal Transduction ◽  
Quorum Sensing ◽  
Plant Pathogen ◽  
Bacterial Species ◽  
Homoserine Lactone ◽  
Signal Molecules ◽  
Acyl Homoserine Lactone ◽  
Interspecies Interactions ◽  
Major Factors

ABSTRACT Bacterial communities can sense their neighbors, regulating group behaviors in response to cell density and environmental changes. The diversity of signaling networks in a single species has been postulated to allow custom responses to different stimuli; however, little is known about how multiple signals are integrated and the implications of this integration in different ecological contexts. In the plant pathogen Pectobacterium wasabiae (formerly Erwinia carotovora), two signaling networks—the N-acyl homoserine lactone (AHL) quorum-sensing system and the Gac/Rsm signal transduction pathway—control the expression of secreted plant cell wall-degrading enzymes, its major virulence determinants. We show that the AHL system controls the Gac/Rsm system by affecting the expression of the regulatory RNA RsmB. This regulation is mediated by ExpR2, the quorum-sensing receptor that responds to the P. wasabiae cognate AHL but also to AHLs produced by other bacterial species. As a consequence, this level of regulation allows P. wasabiae to bypass the Gac-dependent regulation of RsmB in the presence of exogenous AHLs or AHL-producing bacteria. We provide in vivo evidence that this pivotal role of RsmB in signal transduction is important for the ability of P. wasabiae to induce virulence in response to other AHL-producing bacteria in multispecies plant lesions. Our results suggest that the signaling architecture in P. wasabiae was coopted to prime the bacteria to eavesdrop on other bacteria and quickly join the efforts of other species, which are already exploiting host resources. IMPORTANCE Quorum-sensing mechanisms enable bacteria to communicate through small signal molecules and coordinate group behaviors. Often, bacteria have various quorum-sensing receptors and integrate information with other signal transduction pathways, presumably allowing them to respond to different ecological contexts. The plant pathogen Pectobacterium wasabiae has two N-acyl homoserine lactone receptors with apparently the same regulatory functions. Our work revealed that the receptor with the broadest signal specificity is also responsible for establishing the link between the main signaling pathways regulating virulence in P. wasabiae. This link is essential to provide P. wasabiae with the ability to induce virulence earlier in response to higher densities of other bacterial species. We further present in vivo evidence that this novel regulatory link enables P. wasabiae to join related bacteria in the effort to degrade host tissue in multispecies plant lesions. Our work provides support for the hypothesis that interspecies interactions are among the major factors influencing the network architectures observed in bacterial quorum-sensing pathways. IMPORTANCE Quorum-sensing mechanisms enable bacteria to communicate through small signal molecules and coordinate group behaviors. Often, bacteria have various quorum-sensing receptors and integrate information with other signal transduction pathways, presumably allowing them to respond to different ecological contexts. The plant pathogen Pectobacterium wasabiae has two N-acyl homoserine lactone receptors with apparently the same regulatory functions. Our work revealed that the receptor with the broadest signal specificity is also responsible for establishing the link between the main signaling pathways regulating virulence in P. wasabiae. This link is essential to provide P. wasabiae with the ability to induce virulence earlier in response to higher densities of other bacterial species. We further present in vivo evidence that this novel regulatory link enables P. wasabiae to join related bacteria in the effort to degrade host tissue in multispecies plant lesions. Our work provides support for the hypothesis that interspecies interactions are among the major factors influencing the network architectures observed in bacterial quorum-sensing pathways.

scholarly journals Helicobacter pylori FlhA Binds the Sensor Kinase and Flagellar Gene Regulatory Protein FlgS with High Affinity

2015 ◽  
Vol 197 (11) ◽  
pp. 1886-1892 ◽  
Author(s):  
Jennifer Tsang ◽  
Takanori Hirano ◽  
Timothy R. Hoover ◽  
Jonathan L. McMurry
Keyword(s):  
Helicobacter Pylori ◽  
Response Regulator ◽  
Regulatory Protein ◽  
Kinase Domain ◽  
Optical Biosensing ◽  
Content Type ◽  
High Affinity ◽  
Flagellar Assembly ◽  
Flagellar Biogenesis

ABSTRACTFlagellar biogenesis is a complex process that involves multiple checkpoints to coordinate transcription of flagellar genes with the assembly of the flagellum. InHelicobacter pylori, transcription of the genes needed in the middle stage of flagellar biogenesis is governed by RpoN and the two-component system consisting of the histidine kinase FlgS and response regulator FlgR. In response to an unknown signal, FlgS autophosphorylates and transfers the phosphate to FlgR, initiating transcription from RpoN-dependent promoters. In the present study, export apparatus protein FlhA was examined as a potential signal protein. Deletion of its N-terminal cytoplasmic sequence dramatically decreased expression of two RpoN-dependent genes,flaBandflgE. Optical biosensing demonstrated a high-affinity interaction between FlgS and a peptide consisting of residues 1 to 25 of FlhA (FlhANT). TheKD(equilibrium dissociation constant) was 21 nM and was characterized by fast-on (kon= 2.9 × 104M−1s−1) and slow-off (koff= 6.2 × 10−4s−1) kinetics. FlgS did not bind peptides consisting of smaller fragments of the FlhANTsequence. Analysis of binding to purified fragments of FlgS demonstrated that the C-terminal portion of the protein containing the kinase domain binds FlhANT. FlhANTbinding did not stimulate FlgS autophosphorylationin vitro, suggesting that FlhA facilitates interactions between FlgS and other structures required to stimulate autophosphorylation.IMPORTANCEThe high-affinity binding of FlgS to FlhA characterized in this study points to an additional role for FlhA in flagellar assembly. Beyond its necessity for type III secretion, the N-terminal cytoplasmic sequence of FlhA is required for RpoN-dependent gene expression via interaction with the C-terminal kinase domain of FlgS.

scholarly journals Diversification of Campylobacter jejuni Flagellar C-Ring Composition Impacts Its Structure and Function in Motility, Flagellar Assembly, and Cellular Processes

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Louie D. Henderson ◽  
Teige R. S. Matthews-Palmer ◽  
Connor J. Gulbronson ◽  
Deborah A. Ribardo ◽  
Morgan Beeby ◽  
...  
Keyword(s):  
Campylobacter Jejuni ◽  
Content Type ◽  
Cellular Processes ◽  
Spatial Regulation ◽  
Flagellar Motors ◽  
Core Components ◽  
Flagellar Assembly ◽  
And Function ◽  
Conserved Core ◽  
Flagellar Biogenesis

ABSTRACT Bacterial flagella are reversible rotary motors that rotate external filaments for bacterial propulsion. Some flagellar motors have diversified by recruiting additional components that influence torque and rotation, but little is known about the possible diversification and evolution of core motor components. The mechanistic core of flagella is the cytoplasmic C ring, which functions as a rotor, directional switch, and assembly platform for the flagellar type III secretion system (fT3SS) ATPase. The C ring is composed of a ring of FliG proteins and a helical ring of surface presentation of antigen (SPOA) domains from the switch proteins FliM and one of two usually mutually exclusive paralogs, FliN or FliY. We investigated the composition, architecture, and function of the C ring of Campylobacter jejuni, which encodes FliG, FliM, and both FliY and FliN by a variety of interrogative approaches. We discovered a diversified C. jejuni C ring containing FliG, FliM, and both FliY, which functions as a classical FliN-like protein for flagellar assembly, and FliN, which has neofunctionalized into a structural role. Specific protein interactions drive the formation of a more complex heterooligomeric C. jejuni C-ring structure. We discovered that this complex C ring has additional cellular functions in polarly localizing FlhG for numerical regulation of flagellar biogenesis and spatial regulation of division. Furthermore, mutation of the C. jejuni C ring revealed a T3SS that was less dependent on its ATPase complex for assembly than were other systems. Our results highlight considerable evolved flagellar diversity that impacts motor output, biogenesis, and cellular processes in different species. IMPORTANCE The conserved core of bacterial flagellar motors reflects a shared evolutionary history that preserves the mechanisms essential for flagellar assembly, rotation, and directional switching. In this work, we describe an expanded and diversified set of core components in the Campylobacter jejuni flagellar C ring, the mechanistic core of the motor. Our work provides insight into how usually conserved core components may have diversified by gene duplication, enabling a division of labor of the ancestral protein between the two new proteins, acquisition of new roles in flagellar assembly and motility, and expansion of the function of the flagellum beyond motility, including spatial regulation of cell division and numerical control of flagellar biogenesis in C. jejuni. Our results highlight that relatively small changes, such as gene duplications, can have substantial ramifications on the cellular roles of a molecular machine.

scholarly journals Assembly Mechanism of a Supramolecular MS-Ring Complex To Initiate Bacterial Flagellar Biogenesis in Vibrio Species

2020 ◽  
Vol 202 (16) ◽  
Author(s):  
Hiroyuki Terashima ◽  
Keiichi Hirano ◽  
Yuna Inoue ◽  
Takaya Tokano ◽  
Akihiro Kawamoto ◽  
...  
Keyword(s):  
Cytoplasmic Membrane ◽  
Supramolecular Complex ◽  
Ring Formation ◽  
Content Type ◽  
Bacterial Flagellum ◽  
Cell Pole ◽  
Ring Assembly ◽  
Assembly Mechanism ◽  
Ring Complex ◽  
Flagellar Biogenesis

ABSTRACT The bacterial flagellum is an organelle responsible for motility and has a rotary motor comprising the rotor and the stator. Flagellar biogenesis is initiated by the assembly of the MS-ring, a supramolecular complex embedded in the cytoplasmic membrane. The MS-ring consists of a few dozen copies of the transmembrane FliF protein and is an essential core structure that is a part of the rotor. The number and locations of the flagella are controlled by the FlhF and FlhG proteins in some species. However, there is no clarity on the factors initiating MS-ring assembly or on the contributions of FlhF/FlhG to this process. Here, we show that FlhF and a C-ring component, FliG, facilitate Vibrio MS-ring formation. When Vibrio FliF alone was expressed in Escherichia coli cells, MS-ring formation rarely occurred, indicating a requirement of other factors for MS-ring assembly. Consequently, we investigated if FlhF aided FliF in MS-ring assembly. We found that FlhF allowed green fluorescent protein (GFP)-fused FliF to localize at the cell pole in a Vibrio cell, suggesting that it increases local concentration of FliF at the pole. When FliF was coexpressed with FlhF in E. coli cells, the MS-ring was effectively formed, indicating that FlhF somehow contributes to MS-ring formation. The isolated MS-ring structure was similar to that of the MS-ring formed by Salmonella FliF. Interestingly, FliG facilitates MS-ring formation, suggesting that FliF and FliG assist in each other’s assembly into the MS-ring and C-ring. This study aids in understanding the mechanism behind MS-ring assembly using appropriate spatial/temporal regulations. IMPORTANCE Flagellar formation is initiated by the assembly of the FliF protein into the MS-ring complex, which is embedded in the cytoplasmic membrane. The appropriate spatial/temporal control of MS-ring formation is important for the morphogenesis of the bacterial flagellum. Here, we focus on the assembly mechanism of Vibrio FliF into the MS-ring. FlhF, a positive regulator of the number and location of flagella, recruits the FliF molecules at the cell pole and facilitates MS-ring formation. FliG also facilitates MS-ring formation. Our study showed that these factors control flagellar biogenesis in Vibrio by initiating the MS-ring assembly. Furthermore, it also implies that flagellar biogenesis is a sophisticated system linked with the expression of certain genes, protein localization, and a supramolecular complex assembly.

scholarly journals Stochastic transcriptional pulses orchestrate flagellar biosynthesis in Escherichia coli

2020 ◽  
Vol 6 (6) ◽  
pp. eaax0947 ◽  
Author(s):  
J. Mark Kim ◽  
Mayra Garcia-Alcala ◽  
Enrique Balleza ◽  
Philippe Cluzel
Keyword(s):  
Escherichia Coli ◽  
Translational Regulation ◽  
Temporal Dynamics ◽  
Transcriptional Networks ◽  
Cell Level ◽  
E Coli ◽  
Flagellar Biosynthesis ◽  
Flagellar Assembly ◽  
Regulatory Dynamics ◽  
Flagellum Biosynthesis

The classic picture of flagellum biosynthesis in Escherichia coli, inferred from population measurements, depicts a deterministic program where promoters are sequentially up-regulated and are maintained steadily active throughout exponential growth. However, complex regulatory dynamics at the single-cell level can be masked by bulk measurements. Here, we discover that in individual E. coli cells, flagellar promoters are stochastically activated in pulses. These pulses are coordinated within specific classes of promoters and comprise “on” and “off” states, each of which can span multiple generations. We demonstrate that in this pulsing program, the regulatory logic of flagellar assembly dictates which promoters skip pulses. Surprisingly, pulses do not require specific transcriptional or translational regulation of the flagellar master regulator, FlhDC, but instead appears to be essentially governed by an autonomous posttranslational circuit. Our results suggest that even topologically simple transcriptional networks can generate unexpectedly rich temporal dynamics and phenotypic heterogeneities.

scholarly journals Novel Translation Initiation Regulation Mechanism in Escherichia coli ptrB Mediated by a 5′-Terminal AUG

2017 ◽  
Vol 199 (14) ◽  
Author(s):  
Heather J. Beck ◽  
Gary R. Janssen
Keyword(s):  
Escherichia Coli ◽  
Translation Initiation ◽  
Translational Regulation ◽  
Current Knowledge ◽  
Upstream Open Reading Frame ◽  
Model Organisms ◽  
Regulation Mechanism ◽  
Rna Regulation ◽  
Content Type ◽  
E Coli

ABSTRACT Alternative translation initiation mechanisms, distinct from the Shine-Dalgarno (SD) sequence-dependent mechanism, are more prevalent in bacteria than once anticipated. Translation of Escherichia coli ptrB instead requires an AUG triplet at the 5′ terminus of its mRNA. The 5′-terminal AUG (5′-uAUG) acts as a ribosomal recognition signal to attract ribosomes to the ptrB mRNA rather than functioning as an initiation codon to support translation of an upstream open reading frame. ptrB expression exhibits a stronger dependence on the 5′-uAUG than the predicted SD sequence; however, strengthening the predicted ptrB SD sequence relieves the necessity for the 5′-uAUG. Additional sequences within the ptrB 5′ untranslated region (5′-UTR) work cumulatively with the 5′-uAUG to control expression of the downstream ptrB coding sequence (CDS), thereby compensating for the weak SD sequence. Replacement of 5′-UTRs from other mRNAs with the ptrB 5′-UTR sequence showed a similar dependence on the 5′-uAUG for CDS expression, suggesting that the regulatory features contained within the ptrB 5′-UTR are sufficient to control the expression of other E. coli CDSs. Demonstration that the 5′-uAUG present on the ptrB leader mRNA is involved in ribosome binding and expression of the downstream ptrB CDS revealed a novel form of translational regulation. Due to the abundance of AUG triplets at the 5′ termini of E. coli mRNAs and the ability of ptrB 5′-UTR regulation to function independently of gene context, the regulatory effects of 5′-uAUGs on downstream CDSs may be widespread throughout the E. coli genome. IMPORTANCE As the field of synthetic biology continues to grow, a complete understanding of basic biological principles will be necessary. The increasing complexity of the synthetic systems highlights the gaps in our current knowledge of RNA regulation. This study demonstrates that there are novel ways to regulate canonical Shine-Dalgarno-led mRNAs in Escherichia coli, illustrating that our understanding of the fundamental processes of translation and RNA regulation is still incomplete. Even for E. coli, one of the most-studied model organisms, genes with translation initiation mechanisms that do not fit the canonical Shine-Dalgarno sequence paradigm are being revealed. Uncovering diverse mechanisms that control translational expression will allow synthetic biologists to finely tune protein production of desired gene products.

scholarly journals A Two-Component System that Modulates Cyclic-di-GMP Metabolism PromotesLegionella pneumophilaDifferentiation and Viability in Low-Nutrient Conditions

2019 ◽  
Author(s):  
Elisa D. Hughes ◽  
Brenda G. Byrne ◽  
Michele S. Swanson
Keyword(s):  
Life Cycle ◽  
Bacterial Species ◽  
Lifestyle Changes ◽  
Negative Regulator ◽  
Broth Culture ◽  
Cell Type ◽  
Two Component System ◽  
Term Survival ◽  
Component System ◽  
Two Component

ABSTRACTDuring its life cycle, the environmental pathogenLegionella pneumophilaalternates between a replicative and a transmissive cell type when cultured in broth, macrophages, or amoebae. Within a protozoan host,L. pneumophilafurther differentiates into the hardy cell type known as the Mature Infectious Form (MIF). The second messenger cyclic-di-GMP coordinates lifestyle changes in many bacterial species, but its role in theL. pneumophilalife cycle is less understood. Using anin vitrobroth culture model that approximates the intracellular transition from the replicative to transmissive form, here we investigate the contribution toL. pneumophiladifferentiation of a two-component system (TCS) that regulates cyclic-di-GMP metabolism. The TCS is encoded bylpg0278-lpg0277and is co-transcribed withlpg0279, which encodes a protein upregulated in MIF cells. Using agfp-reporter, we demonstrate that the promoter for this operon is RpoS-dependent and induced in nutrient-limiting conditions that do not support replication. The response regulator of the TCS (Lpg0277) is a bifunctional enzyme that both synthesizes and degrades cyclic-di-GMP. Using a panel of site-directed point mutants, we show that cyclic-di-GMP synthesis mediated by a conserved GGDEF domain promotes growth arrest of replicativeL. pneumophila, production of pigment and poly-3-hydroxybutyrate storage granules, and viability in nutrient-limiting conditions. Genetic epistasis tests predict that the MIF protein Lpg0279 acts upstream of the TCS as a negative regulator. Thus,L. pneumophilais equipped with a regulatory network in which cyclic-di-GMP stimulates the switch from a replicative to a resilient state equipped to survive in low-nutrient environments.IMPORTANCEAlthough an intracellular pathogen,L. pneumophilahas developed mechanisms to ensure long-term survival in low-nutrient aqueous conditions. Eradication ofL. pneumophilafrom contaminated water supplies has proven challenging, as outbreaks have been traced to previously remediated systems. Understanding the genetic determinants that supportL. pneumophilapersistence in low-nutrient environments can inform design of remediation methods. Here we characterize a genetic locus that encodes a two-component signaling system (lpg0278-lpg0277) and a putative regulator protein (lpg0279) that modulates production of the messenger molecule cyclic-di-GMP. We show that this locus promotes bothL. pneumophilacell differentiation and survival in nutrient-limiting conditions, thus advancing our understanding of the mechanisms that contribute toL. pneumophilaenvironmental resilience.

Regulation of chemical stress-induced hsp70 gene expression in murine L929 cells

1994 ◽  
Vol 107 (8) ◽  
pp. 2209-2214 ◽  
Author(s):  
R.Y. Liu ◽  
P.M. Corry ◽  
Y.J. Lee
Keyword(s):  
Gene Expression ◽  
Heat Shock ◽  
Negative Regulator ◽  
Transcriptional Level ◽  
Regulation Mechanism ◽  
Chemical Stress ◽  
Hsp70 Gene ◽  
Heat Shock Element ◽  
L929 Cells ◽  
Chemical Treatments

We have investigated the regulation mechanism of chemical stress-induced hsp70 gene expression in murine L929 cells. Our data show that chemical treatments including sodium arsenite, cadmium chloride and sodium salicylate, induced significant synthesis of hsp70 and its mRNA. The induced hsp70 gene expression appears to be regulated at the transcriptional level. A factor (CHBF), which constitutively binds to the heat shock element (HSE) at 37 degrees C, functions like a negative regulator and the heat-induced heat shock factor (HSF) acts as an activator. The chemical treatments that induce significant hsp70 synthesis activate HSF binding to HSE but also dissociate the HSE-CHBF complex. Some chemical treatments, e.g. IPTG, which fail to activate hsp70 gene transcription, still activate HSF binding to HSE. However, in this case, the HSE-CHBF complex remained like that of untreated control cells.

Sign in / Sign up

Export Citation Format

Share Document