Heat Shock Transcription Factor Hsf1 Research Articles

The kinetics of HIV-1 long terminal repeat transcriptional activation resemble those of hsp70 promoter in heat-shock treated HeLa cells

The long terminal repeat (LTR) of human immunodeficiency virus type 1 (HIV-1) is activated under different conditions including heat shock. By using transient transfection assays, we have compared the thermal activation of HIV-1 LTR to that of the promoter of the gene encoding the human stress protein hsp70 which is under the control of the heat shock transcription factor HSF. In these assays, the chloramphenicol acetyl transferase (Cat) gene was used as a reporter gene. Several parameters of the heat stress were analyzed such as the temperature, the duration of heat stress and that of the recovery period. Under every condition tested, we have found that the kinetics of activation of both promoters were very similar. In addition, both showed a similar inhibition by actinomycin D. These results were compared to those obtained with a DNA construct containing the early promoter of SV-40 virus coupled to the Cat gene. In this case, no heat-mediated accumulation of CAT protein was observed, indicating that the transcriptional activation of HIV-1 LTR by heat shock is specific. HIV-1 LTR contains two NF-κB binding elements, involved in the activation of this promoter during oxidative stress, which are sequence related to the heat shock element HSE. However, under all the heat shock conditions tested, we have been unable to detect the binding of any protein to κB elements, suggesting that this site is not directly involved in the thermal activation of HIV-1 LTR. These results indicate that the thermal transcriptional activation of HIV-1 LTR and hsp70 promoters occurs through different mechanisms that are triggered by similar heat shock conditions.

The kinetics of HIV-1 long terminal repeat transcriptional activation resemble those of hsp70 promoter in heat-shock treated HeLa cells

The long terminal repeat (LTR) of human immunodeficiency virus type 1 (HIV-1) is activated under different conditions including heat shock. By using transient transfection assays, we have compared the thermal activation of HIV-1 LTR to that of the promoter of the gene encoding the human stress protein hsp70 which is under the control of the heat shock transcription factor HSF. In these assays, the chloramphenicol acetyl transferase (Cat) gene was used as a reporter gene. Several parameters of the heat stress were analyzed such as the temperature, the duration of heat stress and that of the recovery period. Under every condition tested, we have found that the kinetics of activation of both promoters were very similar. In addition, both showed a similar inhibition by actinomycin D. These results were compared to those obtained with a DNA construct containing the early promoter of SV-40 virus coupled to the Cat gene. In this case, no heat-mediated accumulation of CAT protein was observed, indicating that the transcriptional activation of HIV-1 LTR by heat shock is specific. HIV-1 LTR contains two NF-κB binding elements, involved in the activation of this promoter during oxidative stress, which are sequence related to the heat shock element HSE. However, under all the heat shock conditions tested, we have been unable to detect the binding of any protein to κB elements, suggesting that this site is not directly involved in the thermal activation of HIV-1 LTR. These results indicate that the thermal transcriptional activation of HIV-1 LTR and hsp70 promoters occurs through different mechanisms that are triggered by similar heat shock conditions.

Human heat shock factors 1 and 2 are differentially activated and can synergistically induce hsp70 gene transcription.

Two members of the heat shock transcription factor (HSF) family, HSF1 and HSF2, both function as transcriptional activators of heat shock gene expression. However, the inducible DNA-binding activities of these two factors are regulated by distinct pathways. HSF1 is activated by heat shock and other forms of stress, whereas HSF2 is activated during hemin-induced differentiation of human K562 erythroleukemia cells, suggesting a role for HSF2 in regulating heat shock gene expression under nonstress conditions such as differentiation and development. To understand the distinct regulatory pathways controlling HSF2 and HSF1 activities, we have examined the biochemical and physical properties of the control and activated states of HSF2 and compared these with the properties of HSF1. Our results reveal that the inactive, non-DNA-binding forms of HSF2 and HSF1 exist primarily in the cytoplasm of untreated K562 cells as a dimer and monomer, respectively. This difference in the control oligomeric states suggests that the mechanisms used to control the DNA-binding activities of HSF2 and HSF1 are distinct. Upon activation, both factors acquire DNA-binding activity, oligomerize to a trimeric state, and translocate into the nucleus. Interestingly, we find that simultaneous activation of both HSF2 and HSF1 in K562 cells subjected to hemin treatment followed by heat shock results in the synergistic induction of hsp70 gene transcription, suggesting a novel level of complex regulation of heat shock gene expression.

Human heat shock factors 1 and 2 are differentially activated and can synergistically induce hsp70 gene transcription.

Two members of the heat shock transcription factor (HSF) family, HSF1 and HSF2, both function as transcriptional activators of heat shock gene expression. However, the inducible DNA-binding activities of these two factors are regulated by distinct pathways. HSF1 is activated by heat shock and other forms of stress, whereas HSF2 is activated during hemin-induced differentiation of human K562 erythroleukemia cells, suggesting a role for HSF2 in regulating heat shock gene expression under nonstress conditions such as differentiation and development. To understand the distinct regulatory pathways controlling HSF2 and HSF1 activities, we have examined the biochemical and physical properties of the control and activated states of HSF2 and compared these with the properties of HSF1. Our results reveal that the inactive, non-DNA-binding forms of HSF2 and HSF1 exist primarily in the cytoplasm of untreated K562 cells as a dimer and monomer, respectively. This difference in the control oligomeric states suggests that the mechanisms used to control the DNA-binding activities of HSF2 and HSF1 are distinct. Upon activation, both factors acquire DNA-binding activity, oligomerize to a trimeric state, and translocate into the nucleus. Interestingly, we find that simultaneous activation of both HSF2 and HSF1 in K562 cells subjected to hemin treatment followed by heat shock results in the synergistic induction of hsp70 gene transcription, suggesting a novel level of complex regulation of heat shock gene expression.

Cooperative binding of heat shock transcription factor to the Hsp70 promoter in vivo and in vitro.

The minimal promoter of the Drosophila hsp70 gene contains a TATA box and two nonidentical HSE sequences, HSEI and HSEII, that synergistically activate the promoter. We have examined stereospecific alignment and spatial constraints in this promoter. Similar to deletion of HSEII, insertion in the spacer between the HSEs of 1 to 5 or 11 to 14 nucleotides (nt) reduced promoter activity to about 10%. In contrast, HSEII was capable of contributing to promoter activity when the spacer was either shortened by 2 or 4 nt or extended by 6 to 10 or 16 or 18 nt. Hence, half of the possible helical arrangements of HSEs are compatible, whereas the other half are essentially incompatible with efficient promoter function. HSEII was ineffective when its distance to HSEI was increased by more than 18 nt. In vitro, HSEII is a weak and HSEI a strong binding site for heat shock transcription factor HSF, and HSF binds to HSEII cooperatively. To find out whether the above periodicity reflects cooperative binding of HSF in vivo or represents the need of stereoalignment for synergistic activation of transcription, the weak HSF binding site HSEII was replaced with the strong binding site HSEI. This substitution greatly attenuated promoter periodicity, suggesting that the periodic effects are caused by cooperative binding of HSF to HSEII, and that stereoalignment of HSEs is not required for transcription activation. In agreement, in vitro assays using spacer mutants revealed cooperative binding of purified, recombinant HSF to HSEII with a similar periodicity as observed in vivo. Changing the distance between TATA and the HSEs did not produce promoter periodicity, indicating that stereoalignment of these elements is not important.

Activation of human heat shock genes is accompanied by oligomerization, modification, and rapid translocation of heat shock transcription factor HSF1.

Transcriptional activity of heat shock (hsp) genes is controlled by a heat-activated, group-specific transcription factor(s) recognizing arrays of inverted repeats of the element NGAAN. To date genes for two human factors, HSF1 and HSF2, have been isolated. To define their properties as well as the changes they undergo during heat stress activation, we prepared polyclonal antibodies to these factors. Using these tools, we have shown that human HeLa cells constitutively synthesize HSF1, but we were unable to detect HSF2. In unstressed cells HSF1 is present mainly in complexes with an apparent molecular mass of about 200 kDa, unable to bind to DNA. Heat treatment induces a shift in the apparent molecular mass of HSF1 to about 700 kDa, concomitant with the acquisition of DNA-binding ability. Cross-linking experiments suggest that this change in complex size may reflect the trimerization of monomeric HSF1. Human HSF1 expressed in Xenopus oocytes does not bind DNA, but derepression of DNA-binding activity, as well as oligomerization of HSF1, occurs during heat treatment at the same temperature at which hsp gene expression is induced in this organism, suggesting that a conserved Xenopus protein(s) plays a role in this regulation. Inactive HSF1 resides in the cytoplasm of human cells; on activation it rapidly translocates to a soluble nuclear fraction, and shortly thereafter it becomes associated with the nuclear pellet. On heat shock, activatable HSF1, which might already have been posttranslationally modified in the unstressed cell, undergoes further modification. These different process provide multiple points of regulation of hsp gene expression.

Activation of human heat shock genes is accompanied by oligomerization, modification, and rapid translocation of heat shock transcription factor HSF1.

Transcriptional activity of heat shock (hsp) genes is controlled by a heat-activated, group-specific transcription factor(s) recognizing arrays of inverted repeats of the element NGAAN. To date genes for two human factors, HSF1 and HSF2, have been isolated. To define their properties as well as the changes they undergo during heat stress activation, we prepared polyclonal antibodies to these factors. Using these tools, we have shown that human HeLa cells constitutively synthesize HSF1, but we were unable to detect HSF2. In unstressed cells HSF1 is present mainly in complexes with an apparent molecular mass of about 200 kDa, unable to bind to DNA. Heat treatment induces a shift in the apparent molecular mass of HSF1 to about 700 kDa, concomitant with the acquisition of DNA-binding ability. Cross-linking experiments suggest that this change in complex size may reflect the trimerization of monomeric HSF1. Human HSF1 expressed in Xenopus oocytes does not bind DNA, but derepression of DNA-binding activity, as well as oligomerization of HSF1, occurs during heat treatment at the same temperature at which hsp gene expression is induced in this organism, suggesting that a conserved Xenopus protein(s) plays a role in this regulation. Inactive HSF1 resides in the cytoplasm of human cells; on activation it rapidly translocates to a soluble nuclear fraction, and shortly thereafter it becomes associated with the nuclear pellet. On heat shock, activatable HSF1, which might already have been posttranslationally modified in the unstressed cell, undergoes further modification. These different process provide multiple points of regulation of hsp gene expression.

Temperature regulation in the exercising rabbit.

ARTICLESTemperature regulation in the exercising rabbitMJ Kluger, RR Gonzalez, and JA StolwijkMJ Kluger, RR Gonzalez, and JA StolwijkPublished Online:01 Jan 1973https://doi.org/10.1152/ajplegacy.1973.224.1.130MoreSectionsPDF (1 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformationCited ByWelfare of domestic birds and rabbits transported in containersEFSA Journal, Vol. 20, No. 9Advantage to lower body temperatures for a small mammal ( Rattus fuscipes ) experiencing chronic cold15 October 2010 | Journal of Mammalogy, Vol. 91, No. 5Is the large size of the pinna of the ear of the European hare ( Lepus europaeus ) due to its role in thermoregulation or in anterior capital shock absorption?Journal of Morphology, Vol. 36Selective brain cooling: a multiple regulatory mechanismJournal of Thermal Biology, Vol. 29, No. 7-8Selective Brain Cooling and Thermoregulatory Set-PointJournal of Basic and Clinical Physiology and Pharmacology, Vol. 9, No. 1Tissue-specific differences in heat shock protein hsc70 and hsp70 in the control and hyperthermic rabbitJournal of Cellular Physiology, Vol. 170, No. 2Mechanisms of Heat Exchange: Biophysics and Physiology1 January 2011In vivo activation of neural heat shock transcription factor HSF1 by a physiologically relevant increase in body temperatureJournal of Neuroscience Research, Vol. 44, No. 1Expression of mRNA species encoding heat shock protein 90 (hsp90) in control and hyperthermic rabbit brainJournal of Neuroscience Research, Vol. 43, No. 3Thermoregulatory vasomotor reactions during endotoxin fever in guinea pigsJournal of Thermal Biology, Vol. 20, No. 5Effect of hyperthermia on blood constituents in the domestic rabbit (Lepus cuniculus)Journal of Thermal Biology, Vol. 19, No. 6Temporal and spatial distribution of heat shock mRNA and protein (hsp70) in the rabbit cerebellum in response to hyperthermiaJournal of Neuroscience Research, Vol. 36, No. 4Expression of heat shock genes (hsp70) in the rabbit spinal cord: Localization of constitutive and hyperthermia-inducible mRNA speciesJournal of Neuroscience Research, Vol. 31, No. 4The circadian rhythm of body temperaturePhysiology & Behavior, Vol. 51, No. 3ANALYSIS OF PROTEIN SYNTHESIS IN THE MAMMALIAN BRAIN USING LSD AND HYPERTHERMIA AS EXPERIMENTAL PROBESOral Thermal-Induced Flushing in Erythematotelangiectatic RosaceaJournal of Investigative Dermatology, Vol. 76, No. 1Thermal responses to preoptic heating and ambient temperature in unrestrained rabbitsJournal of Thermal Biology, Vol. 1, No. 1Energy Balance in the Resting and Exercising RabbitTemperature regulation: The spinal cord as a site of extrahypothalamic thermoregulatory functions More from this issue > Volume 224Issue 1January 1973Pages 130-135 Copyright & PermissionsCopyright © 1973 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1973.224.1.130PubMed4566848History Published online 1 January 1973 Published in print 1 January 1973 Metrics