Role of Heat Shock Factors in Stress-Induced Transcription

Abstract

Heat shock proteins (HSP) are rapidly induced after stresses such as heat shock and accumulate at high concentrations in cells. HSP induction involves a family of heat shock transcription factors (HSF) that bind the heat shock elements of the HSP genes and mediate transcription in trans. We discuss methods for the study of HSP binding to HSP promoters and the consequent increases in HSP gene expression in vitro and in vivo. Keywordsheat; shock; factor; binding; transcription (1) IntroductionHeat shock factor (HSF) was first discovered in yeast as a sequence specific transcription factor that binds to the promoters of heat shock protein (HSP) genes 1 . HSF was shown to bind as a trimer to three inverted repeats of the sequence nGAAn at high affinity, an activity that was later shown in Drosophila HSF and human HSF1 2-5 . In more complex organisms, there at least 4 members of the family in avian and mammalian species and multiple members in higher plants [6][7][8][9][10][11] . The current consensus in mammalian cells is that HSF1 is the 2 Communicating author: Stuart K Calderwood, scalderw@bidmc.harvard.edu; telephone 617-667-0970. 1 Equal contributor(1) The EMSA technique has the advantages that it is rapid, sensitive and straightforward to carry out. For assessing the significance of the transcription factor-response element interaction, it is however lacking in that response elements in chromatin are wound along nucleaomes and may not be available for binding. The EMSA reaction is carried out using naked DNA. In addition as ChIP on CHIP and ChIP-seq studies begin to accumulate it is evident that response elements for particular factors are more flexible than suspected from early studies.(2) Some of these problems can be avoided using the ChIP assay that measures HSF binding to chromosomal DNA in vivo. This technique is highly dependent on availability of high affinity and specific antibodies for transcription factors. This can be overcome by overexpression of the factor with a seuqence tag and carrying out ChIP with anti-TAG antibody. However this can introduce potential artifacts involved with protein overexpression. (3) To assess the results of HSF-DNA binding we have used two approaches. We have used transfection of reporter constructs containing either HSP promoters or HSE coupled to reporter genes CAT or luciferase. The assays have the advantages of being rapid and permitting accumulation of plentiful data. The promoter portion of the construct can be tailored to assess the activity of a single transcription factor such as HSF1. The assay is however indirect and does not measure the transcription of the native, chromosomallyembedded gene. There are other potential complications, as reporters require to be translated and yield enzymatically active proteins. (4) Transcriptional rate of HSP genes such can be assess directly by run-on assay. This assay indicates that joint activities of all response elements in the HSP gene promoters. Although genes such as HSP70B respond only to HSF1 or heat shock, ot...

Heat Stress Impairs the Physiological Responses and Regulates Genes Coding for Extracellular Exosomal Proteins in Rat

“…However, Inmt showed an opposite trend in vivo and in vitro, which warrants further research by increasing samples size and technique repeats. The expression of Hspa1b first increased and then decreased slightly at H60 and H120, which is consistent with other HSP family expression levels under HS [51] ( Figure 9D). The relative protein level of Atp5f1 in HS groups was all higher (P < 0.01) than that in control groups ( Figure 9D) and combined with the expression level of Atp5f1 gene at H60 and H120 conditions ( Figure 9C), demonstrating that HS has a delayed effect on the expression of proteins.…”

“…Genes 2020, 11, x FOR PEER REVIEW 16 of 23 H120, which is consistent with other HSP family expression levels under HS [51] ( Figure 9D). The relative protein level of Atp5f1 in HS groups was all higher (P < 0.01) than that in control groups ( Figure 9D) and combined with the expression level of Atp5f1 gene at H60 and H120 conditions ( Figure 9C), demonstrating that HS has a delayed effect on the expression of proteins.…”

Come Together: Protein Assemblies, Aggregates and the Sarcostat at the Heart of Cardiac Myocyte Homeostasis

“…A unifying factor across all heat shock proteins is HSF-1, the master regulator of the heat shock response in eukaryotes (Gomez-Pastor et al, 2018); which was demonstrated to be essential for thermos-tolerance in mammalian systems using a targeted genetic approach (McMillan et al, 1998). The HSF family of transcription factors (HSF1-6 in humans) appears to not only drive the various heat shock proteins but also induce a concerted array of stress response genes that respond to a variety of stimuli, including heat, oxidative stress, metals and proteotoxicity (Murshid et al, 2018). In response to stress, inactive monomeric HSF-1 is activated resulting in formation of a DNA-binding homotrimer via leucine-zipper domains.…”

Genome-Wide Identification and Expression Analysis of Heat Shock Transcription Factor Family in Chenopodium quinoa Willd

“…CqHsf13 and CqHsf14 belonging to the A4 subgroup had relatively high expressions in all five organs, which was also reported in other plant species [35]. For example, the AtHsfA1 in arabidopsis, and MdHsfA1a, MdHsfA1d, MdHsfB1a in apple as well as HsfA1 and HsfA8 genes in wheat were found to be constitutive expression in the tested organs [36][37][38]. The high expression of CqHsf genes in most tissues indicates that these heat shock transcription factors might be widely involved in the growth and development processes.…”

“…It is well known that the expression levels of Hsf genes are significantly affected by heat and other stresses in plants [16,38]. In this study, we also analyze the expression profiles of CqHsf genes under various stress conditions to identify the stress-responsive candidates.…”