scholarly journals The heat-shock transcription factor HSF1 is rapidly activated by either hyper- or hypo-osmotic stress in mammalian cells

1997 ◽  
Vol 327 (2) ◽  
pp. 341-347 ◽  
Author(s):  
Lorraine CARUCCIO ◽  
Sangwoo BAE ◽  
Alice Yee-Chang LIU ◽  
Kuang Yu CHEN
Keyword(s):  
Transcription Factor ◽  
Protein Synthesis ◽  
Heat Shock ◽  
Dna Binding ◽  
Osmotic Stress ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Binary Solution ◽  
Binding Activity ◽  
Dna Binding 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.

scholarly journals Rapid activation of the heat shock transcription factor, HSF1, by hypo-osmotic stress in mammalian cells

1995 ◽  
Vol 307 (2) ◽  
pp. 347-352 ◽  
Author(s):  
L E Huang ◽  
L Caruccio ◽  
A Y Liu ◽  
K Y Chen
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Osmotic Stress ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Environmental Changes ◽  
Binding Activity ◽  
Heat Shock Transcription Factor ◽  
Hypotonic Medium ◽  
Hsp70 Mrna

Osmoregulation is important to living organisms for survival in responding to environmental changes of water and ionic strength. We demonstrated here for the first time that exposure of HeLa cells to a hypotonic medium (30% growth medium and 70% water) prominently induced the binding activity of the heat shock transcription factor (HSF). Pretreatment of cells with cycloheximide did not inhibit the induction of HSF-binding activity, indicating that the mechanisms of induction are independent of new protein synthesis. The magnitude of hypo-osmotic stress-induced HSF-binding activity was comparable with that induced by heat shock. The induction, as monitored by gel-mobility-shift assay, occurred within 5 min of hypo-osmotic stress and persisted at least up to 4 h in HeLa cells under the hypotonic conditions. Addition of sorbitol to the hypotonic medium abolished HSF activation. Hypo-osmotic stress-induced HSF binding could also be demonstrated in HeLa cells maintained in simple sorbitol solution by decreasing the sorbitol concentration from 300 mM to 200 mM or less. Competition analysis suggests that the effects of hypo-osmotic stress on HSF-binding activity was specific. Cross-linking experiments and Western-blot analysis demonstrated that hypo-osmotic stress induced trimerization of human heat shock factor 1 (HSF1) in intact HeLa cells, suggesting that trimer formation of HSF1 was responsible for inducing HSF-binding activity in hypo-osmotically stressed cells. However, unlike heat shock response, the activation of HSF by hypo-osmotic stress did not lead to accumulation of hsp70 mRNA in HeLa cells.

A single polypeptide possesses the binding and transcription activities of the adenovirus major late transcription factor

1986 ◽  
Vol 6 (12) ◽  
pp. 4723-4733
Author(s):  
L A Chodosh ◽  
R W Carthew ◽  
P A Sharp
Keyword(s):  
Transcription Factor ◽  
Dna Binding ◽  
Binding Site ◽  
Rna Polymerase Ii ◽  
Sodium Dodecyl ◽  
Binding Activity ◽  
Affinity Column ◽  
Dna Binding Activity ◽  
Dna Fragment

A simple approach has been developed for the unambiguous identification and purification of sequence-specific DNA-binding proteins solely on the basis of their ability to bind selectively to their target sequences. Four independent methods were used to identify the promoter-specific RNA polymerase II transcription factor MLTF as a 46-kilodalton (kDa) polypeptide. First, a 46-kDa protein was specifically cross-linked by UV irradiation to a body-labeled DNA fragment containing the MLTF binding site. Second, MLTF sedimented through glycerol gradients at a rate corresponding to a protein of native molecular weight 45,000 to 50,000. Third, a 46-kDa protein was specifically retained on a biotin-streptavidin matrix only when the DNA fragment coupled to the matrix contained the MLTF binding site. Finally, proteins from the most highly purified fraction which were eluted and renatured from the 44- to 48-kDa region of a sodium dodecyl sulfate-polyacrylamide gel exhibited both binding and transcription-stimulatory activities. The DNA-binding activity was purified 100,000-fold by chromatography through three conventional columns plus a DNA affinity column. Purified MLTF was characterized with respect to the kinetic and thermodynamic properties of DNA binding. These parameters indicate a high degree of occupancy of MLTF binding sites in vivo.

Interaction between heat shock factor and hsp70 is insufficient to suppress induction of DNA-binding activity in vivo

1994 ◽  
Vol 14 (10) ◽  
pp. 6552-6560
Author(s):  
S K Rabindran ◽  
J Wisniewski ◽  
L Li ◽  
G C Li ◽  
C Wu
Keyword(s):  
Heat Shock ◽  
Dna Binding ◽  
Heat Shock Proteins ◽  
Expression System ◽  
Stress Protein ◽  
Binding Activity ◽  
Protein Family ◽  
Oligomeric State ◽  
Dna Binding Activity ◽  
Shock Proteins

The intracellular level of free heat shock proteins, in particular the 70-kDa stress protein family, has been suggested to be the basis of an autoregulatory mechanism by which the cell measures the level of thermal stress and regulates the synthesis of heat shock proteins. It has been proposed that the DNA-binding and oligomeric state of the heat shock transcription factor (HSF) is a principal step in the induction pathway that is responsive to the level of 70-kDa stress protein. To test this hypothesis, we investigated the association between HSF and 70-kDa stress protein by means of a coimmunoprecipitation assay. We found that 70-kDa stress proteins associate to similar extents with both latent and active forms of HSF, although unlike other 70-kDa stress protein substrates, the association with HSF was not significantly disrupted in the presence of ATP. Gel mobility shift assays indicated that active HSF trimers purified from a bacterial expression system could not be substantially deactivated in vitro with purified 70-kDa stress protein and ATP. In addition, elevated concentrations of hsp70 alone could not significantly inhibit induction of the DNA-binding activity of endogenous HSF in cultured rat cells, and the induction was also not inhibited in cultured rat cells or Drosophila cells containing elevated levels of all members of the heat shock protein family. However, the deactivation of HSF to the non-DNA-binding state after prolonged heat stress or during recovery could be accelerated by increased levels of heat shock proteins. Hence, the level of heat shock proteins may affect the rate of disassembly of HSF trimers, but another mechanism, as yet undefined, appears to control the onset of the oligomeric transitions.

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