Stage-specific alternative splicing of the heat-shock transcription factor during the life-cycle of Schistosoma mansoni

Parasitology ◽  
2004 ◽  
Vol 129 (5) ◽  
pp. 587-596 ◽  
Author(s):  
D. RAM ◽  
E. ZIV ◽  
F. LANTNER ◽  
V. LARDANS ◽  
I. SCHECHTER
Keyword(s):  
Amino Acids ◽  
Transcription Factor ◽  
Alternative Splicing ◽  
Heat Shock ◽  
Dna Binding ◽  
Schistosoma Mansoni ◽  
Structural Diversity ◽  
Heat Shock Transcription Factor ◽  
Functional Evaluation ◽  
Specific Alternative

Stage-specific alternative splicing of the heat-shock transcription factor of Schistosoma mansoni (SmHSF) generates isoforms with structural diversity that may modulate the activity of SmHSF at different life-stages, and thus may regulate the expression of different genes at different developmental stages. RT-PCR, cloning and DNA-sequence analyses showed stage-specific alternative splicing inside the DNA-binding domain (DBD) involving introns I1 and I2, and beyond the DBD involving introns I4a and I7. Retention of introns I2 and I4a would inactivate SmHSF since they contain termination codons. Retention of intron I1 would add 11 amino acids inside the DBD and may change the DNA-binding specificity of SmHSF; intron I7 would add 13 amino acids to the effector region of HSF. Retention of introns was more pronounced in cercariae (larval stage living in water) than in adult worms (parasitic form in mammals). The isoforms were expressed in bacteria, but functional evaluation was not feasible, because only the isoform lacking introns was soluble while isoforms with introns were insoluble. However, stage-specific alternative splicing that changed HSF function in vivo was evidenced in intact cercariae. The cercarial SmHSF mRNA was enriched with introns I2 and I4a that contain termination codons. Therefore, translation of the SmHSF mRNA was impaired, and the SmHSF protein was undetectable. Consequently, the HSP70 gene could not be transcribed, and the HSP70 mRNA was missing. Alternative splicing was observed for short DNA segments (33–45 bp) bound by splice signals, located in the coding region. These are not bona fida exons since they are not flanked by introns. Yet, they are not regular introns since they are often found in mature mRNA. Alternative splicing of these DNA segments caused structural diversity that could modulate the function of the gene product.

scholarly journals 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.

1994 ◽  
Vol 14 (11) ◽  
pp. 7557-7568 ◽  
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.

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

1994 ◽  
Vol 14 (11) ◽  
pp. 7557-7568
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.

scholarly journals The DNA-binding activity of the human heat shock transcription factor is regulated in vivo by hsp70.

1993 ◽  
Vol 13 (9) ◽  
pp. 5427-5438 ◽  
Author(s):  
D D Mosser ◽  
J Duchaine ◽  
B Massie
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Dna Binding ◽  
Elevated Temperatures ◽  
Active Role ◽  
Heat Shock Transcription Factor ◽  
Response To Treatment ◽  
Promoter Element ◽  
Heat Shock Promoter

The human heat shock transcription factor (HSF) is maintained in an inactive non-DNA-binding form under nonstress conditions and acquires the ability to bind specifically to the heat shock promoter element in response to elevated temperatures or other conditions that disrupt protein structure. Here we show that constitutive overexpression of the major inducible heat shock protein, hsp70, in transfected human cells reduces the extent of HSF activation after a heat stress. HSF activation was inhibited more strongly in clones that express higher levels of hsp70. These results demonstrate that HSF activity is negatively regulated in vivo by hsp70 and suggest that the cell might sense elevated temperature as a decreased availability of hsp70. HSF activation in response to treatment with sodium arsenite or the proline analog azetidine was also depressed in hsp70-expressing cells relative to that in the nontransfected control cells. As well, the level of activated HSF decreased more rapidly in the hsp70-expressing clones when the cells were heat shocked and returned to 37 degrees C. These results suggest that hsp70 could play an active role in the conversion of HSF back to a conformation that does not bind the heat shock promoter element during the attenuation of the heat shock response.

scholarly journals Multiple layers of regulation of human heat shock transcription factor 1.

1995 ◽  
Vol 15 (8) ◽  
pp. 4319-4330 ◽  
Author(s):  
J Zuo ◽  
D Rungger ◽  
R Voellmy
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Dna Binding ◽  
Cell Activation ◽  
Transcription Activation ◽  
Heat Shock Transcription Factor ◽  
Activation Domain ◽  
Sequence Element ◽  
Transcription Activation Domain ◽  
Transcription Factor 1

Upon heat stress, monomeric human heat shock transcription factor 1 (hHSF1) is converted to a trimer, acquires DNA-binding ability, is transported to the nucleus, and becomes transcriptionally competent. It was not known previously whether these regulatory changes are caused by a single activation event or whether they occur independently from one another, providing a multilayered control that may prevent inadvertant activation of hHSF1. Comparison of wild-type and mutant hHSF1 expressed in Xenopus oocytes and human HeLa cells suggested that retention of hHSF1 in the monomeric form depends on hydrophobic repeats (LZ1 to LZ3) and a carboxy-terminal sequence element in hHSF1 as well as on the presence of a titratable factor in the cell. Oligomerization of hHSF1 appears to induce DNA-binding activity as well as to uncover an amino-terminally located nuclear localization signal. A mechanism distinct from that controlling oligomerization regulates the transcriptional competence of hHSF1. Components of this mechanism were mapped to a region, including LZ2 and nearby sequences downstream from LZ2, that is clearly separated from the carboxy-terminally located transcription activation domain(s). We propose the existence of a fold-back structure that masks the transcription activation domain in the unstressed cell but is opened up by modification of hHSF1 and/or binding of a factor facilitating hHSF1 unfolding in the stressed cell. Activation of hHSF1 appears to involve at least two independently regulated structural transitions.

scholarly journals Characterization of a novel chicken heat shock transcription factor, heat shock factor 3, suggests a new regulatory pathway.

1993 ◽  
Vol 13 (4) ◽  
pp. 1983-1997 ◽  
Author(s):  
A Nakai ◽  
R I Morimoto
Keyword(s):  
Transcription Factor ◽  
Heat Shock ◽  
Dna Binding ◽  
Heat Shock Transcription Factor ◽  
Heat Shock Gene ◽  
Regulatory Sequences ◽  
Regulatory Pathway ◽  
Binding Properties ◽  
Dna Binding Properties

We have cloned three avian heat shock transcription factor (HSF) genes corresponding to a novel factor, HSF3, and the avian homologs of mammalian HSF1 and HSF2. The predicted amino acid sequence of HSF3 is approximately 40% related to the sequence of HSF1 and HSF2. The sequences for all three factors exhibit extensive identify in the DNA binding motifs and the heptad repeats of hydrophobic amino acids which are common to all eukaryotic HSFs. Despite these overall similarities, each avian HSF exhibits distinct DNA binding properties. HSF2 when expressed in vitro binds constitutively to the heat shock element promoter sequence, whereas neither HSF1 nor HSF3 expressed in vitro binds to DNA. HSF1 DNA binding is induced upon heat shock or treatment with nonionic detergents, whereas the DNA binding properties of HSF3 are not induced by these conditions in vitro. These results suggest that HSF3 activation may involve an induction pathway distinct from the traditional forms of heat shock gene induction. HSF3 DNA binding activity, however, is obtained when the carboxyl-terminal region including the distal heptad repeat is deleted, indicating the presence of negative cis-regulatory sequences. The HSF3 message, like HSF1 and HSF2 messages, is coexpressed during development and in most tissues, which suggests a general role for the regulatory pathway involving HSF3.

Activation of heat shock transcription factor 1 to a DNA binding form during the G1 phase of the cell cycle

1999 ◽  
Vol 4 (1) ◽  
pp. 36 ◽  
Author(s):  
Jacqueline L. Bruce ◽  
Changmin Chen ◽  
Yue Xie ◽  
Rong Zhong ◽  
Yi-qun Wang ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Heat Shock ◽  
Dna Binding ◽  
Heat Shock Transcription Factor ◽  
G1 Phase ◽  
Transcription Factor 1
Sign in / Sign up

Export Citation Format

Share Document