The Heat Shock Transcription Factor in Liver Exists in a Form That Has DNA Binding Activity But No Transcriptional Activity

Osmoregulation, the cellular response to environmental changes of osmolarity and ionic strength, is important for the survival of living organisms. We have demonstrated previously that an exposure of mammalian cells to hypo-osmotic stress, either in growth medium (30% growth medium and 70% water) or in binary solution containing sorbitol and water, prominently induced the DNA-binding activity of the heat-shock transcription factor (HSF1) [Huang, Caruccio, Liu and Chen (1995) Biochem. J. 307, 347-352]. Since hyperosmotic and hypo-osmotic stress usually elicit opposite biological responses, we wondered what would be the effect of hyperosmotic stress on HSF activation. In this study we have examined the HSF DNA-binding activity in HeLa cells maintained in the sorbitol/water binary solution over a wide concentration range (0.1-0.9 M) and in Dulbecco's medium supplemented with sorbitol or NaCl. We found that HSF-binding activity could be induced prominently under both hypo-osmotic (0.1-0.25 M) and hyperosmotic conditions (0.50-0.90 M). In both cases, HSF activation was observed within 5 min after changing the osmotic pressure. The activation was accompanied by both HSF trimerization and nuclear translocation, and appeared to be independent of protein synthesis. The effects of hypo- or hyper-osmotic stress on HSF activation could be reversed once the cells were returned to iso-osmotic conditions (0.30 M) with a half-life () of 25 min or less. This rapid turnover of the osmotic-stress-induced HSF-binding activity was inhibited by cycloheximide, a potent inhibitor of protein synthesis. Unlike heat shock, activation of HSF by either hypo- or hyper-osmotic stress did not lead to an accumulation of heat-shock protein 70 (HSP70) mRNA in HeLa cells. We propose that HSF activation during osmotic stress may serve physiological functions independent of the synthesis of heat-shock proteins.

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A transcriptional repressive role for epithelial-specific ETS factor ELF3 on oestrogen receptor alpha in breast cancer cells

Biochemical Journal ◽

10.1042/bcj20160019 ◽

2016 ◽

Vol 473 (8) ◽

pp. 1047-1061 ◽

Cited By ~ 14

Author(s):

Vijaya Narasihma Reddy Gajulapalli ◽

Venkata Subramanyam Kumar Samanthapudi ◽

Madhusudana Pulaganti ◽

Saratchandra Singh Khumukcham ◽

Vijaya Lakhsmi Malisetty ◽

...

Keyword(s):

Breast Cancer ◽

Transcription Factor ◽

Dna Binding ◽

Cancer Cells ◽

Oestrogen Receptor ◽

Breast Cancer Cells ◽

Transcriptional Activity ◽

Ectopic Expression ◽

Binding Activity ◽

Dna Binding Activity

Oestrogen receptor-α (ERα) is a ligand-dependent transcription factor that primarily mediates oestrogen (E2)-dependent gene transcription required for mammary gland development. Coregulators critically regulate ERα transcription functions by directly interacting with it. In the present study, we report that ELF3, an epithelial-specific ETS transcription factor, acts as a transcriptional repressor of ERα. Co-immunoprecipitation (Co-IP) analysis demonstrated that ELF3 strongly binds to ERα in the absence of E2, but ELF3 dissociation occurs upon E2 treatment in a dose- and time-dependent manner suggesting that E2 negatively influences such interaction. Domain mapping studies further revealed that the ETS (E-twenty six) domain of ELF3 interacts with the DNA binding domain of ERα. Accordingly, ELF3 inhibited ERα’s DNA binding activity by preventing receptor dimerization, partly explaining the mechanism by which ELF3 represses ERα transcriptional activity. Ectopic expression of ELF3 decreases ERα transcriptional activity as demonstrated by oestrogen response elements (ERE)-luciferase reporter assay or by endogenous ERα target genes. Conversely ELF3 knockdown increases ERα transcriptional activity. Consistent with these results, ELF3 ectopic expression decreases E2-dependent MCF7 cell proliferation whereas ELF3 knockdown increases it. We also found that E2 induces ELF3 expression in MCF7 cells suggesting a negative feedback regulation of ERα signalling in breast cancer cells. A small peptide sequence of ELF3 derived through functional interaction between ERα and ELF3 could inhibit DNA binding activity of ERα and breast cancer cell growth. These findings demonstrate that ELF3 is a novel transcriptional repressor of ERα in breast cancer cells. Peptide interaction studies further represent a novel therapeutic option in breast cancer therapy.

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Faculty Opinions recommendation of Transcription coactivator CBP has direct DNA binding activity and stimulates transcription factor DNA binding through small domains.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1009156.119557 ◽

2002 ◽

Author(s):

Gourisankar Ghosh

Keyword(s):

Transcription Factor ◽

Dna Binding ◽

Binding Activity ◽

Dna Binding Activity ◽

Transcription Coactivator

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Activation of the DNA-binding ability of human heat shock transcription factor 1 may involve the transition from an intramolecular to an intermolecular triple-stranded coiled-coil structure.

Molecular and Cellular Biology ◽

10.1128/mcb.14.11.7557 ◽

1994 ◽

Vol 14 (11) ◽

pp. 7557-7568 ◽

Cited By ~ 126

Author(s):

J Zuo ◽

R Baler ◽

G Dahl ◽

R Voellmy

Keyword(s):

Transcription Factor ◽

Heat Stress ◽

Heat Shock ◽

Dna Binding ◽

Hydrophobic Interactions ◽

Coiled Coil ◽

Heat Shock Transcription Factor ◽

Single Amino Acid ◽

Binding Ability ◽

Heat Shock Element

Heat stress regulation of human heat shock genes is mediated by human heat shock transcription factor hHSF1, which contains three 4-3 hydrophobic repeats (LZ1 to LZ3). In unstressed human cells (37 degrees C), hHSF1 appears to be in an inactive, monomeric state that may be maintained through intramolecular interactions stabilized by transient interaction with hsp70. Heat stress (39 to 42 degrees C) disrupts these interactions, and hHSF1 homotrimerizes and acquires heat shock element DNA-binding ability. hHSF1 expressed in Xenopus oocytes also assumes a monomeric, non-DNA-binding state and is converted to a trimeric, DNA-binding form upon exposure of the oocytes to heat shock (35 to 37 degrees C in this organism). Because endogenous HSF DNA-binding activity is low and anti-hHSF1 antibody does not recognize Xenopus HSF, we employed this system for mapping regions in hHSF1 that are required for the maintenance of the monomeric state. The results of mutagenesis analyses strongly suggest that the inactive hHSF1 monomer is stabilized by hydrophobic interactions involving all three leucine zippers which may form a triple-stranded coiled coil. Trimerization may enable the DNA-binding function of hHSF1 by facilitating cooperative binding of monomeric DNA-binding domains to the heat shock element motif. This view is supported by observations that several different LexA DNA-binding domain-hHSF1 chimeras bind to a LexA-binding site in a heat-regulated fashion, that single amino acid replacements disrupting the integrity of hydrophobic repeats render these chimeras constitutively trimeric and DNA binding, and that LexA itself binds stably to DNA only as a dimer but not as a monomer in our assays.

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Identification of a novel determinant for basic domain-leucine zipper DNA binding activity in the acute-phase inducible nuclear factor-interleukin-6 transcription factor.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(17)34066-8 ◽

1994 ◽

Vol 269 (14) ◽

pp. 10341-10351

Author(s):

A.R. Brasier ◽

A. Kumar

Keyword(s):

Transcription Factor ◽

Dna Binding ◽

Acute Phase ◽

Interleukin 6 ◽

Leucine Zipper ◽

Binding Activity ◽

Nuclear Factor ◽

Basic Domain ◽

Dna Binding Activity

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Glycogen Synthase Kinase 3β and Extracellular Signal-Regulated Kinase Inactivate Heat Shock Transcription Factor 1 by Facilitating the Disappearance of Transcriptionally Active Granules after Heat Shock

Molecular and Cellular Biology ◽

10.1128/mcb.18.11.6624 ◽

1998 ◽

Vol 18 (11) ◽

pp. 6624-6633 ◽

Cited By ~ 118

Author(s):

Bin He ◽

Yong-Hong Meng ◽

Nahid F. Mivechi

Keyword(s):

Transcription Factor ◽

Heat Shock ◽

Transcriptional Activity ◽

Glycogen Synthase ◽

Heat Shock Transcription Factor ◽

Glycogen Synthase Kinase 3Β ◽

Extracellular Signal Regulated Kinase ◽

Extracellular Signal ◽

Gsk 3Β ◽

Transcription Factor 1

ABSTRACT Heat shock transcription factor 1 (HSF-1) activates the transcription of heat shock genes in eukaryotes. Under normal physiological growth conditions, HSF-1 is a monomer. Its transcriptional activity is repressed by constitutive phosphorylation. Upon activation, HSF-1 forms trimers, acquires DNA binding activity, increases transcriptional activity, and appears as punctate granules in the nucleus. In this study, using bromouridine incorporation and confocal laser microscopy, we demonstrated that newly synthesized pre-mRNAs colocalize to the HSF-1 punctate granules after heat shock, suggesting that these granules are sites of transcription. We further present evidence that glycogen synthase kinase 3β (GSK-3β) and extracellular signal-regulated kinase mitogen-activated protein kinase (ERK MAPK) participate in the down regulation of HSF-1 transcriptional activity. Transient increases in the expression of GSK-3β facilitate the disappearance of HSF-1 punctate granules and reduce hsp-70 transcription after heat shock. We have also shown that ERK is the priming kinase for GSK-3β. Taken together, these results indicate that GSK-3β and ERK MAPK facilitate the inactivation of activated HSF-1 after heat shock by dispersing HSF-1 from the sites of transcription.

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