Dataset Information

Glutamine-mediated dual regulation of heat shock transcription factor-1 activation and expression.

ABSTRACT:

Background

Regulation of transcriptional activity of heat shock factor-1 (HSF1) is widely thought to be the main point of control for heat shock protein (Hsp) expression.

Results

Glutamine increases Hsf1 gene transcription in a C/EBP?-dependent manner and up-regulates HSF1 activity.

Conclusion

Glutamine is an activator for both HSF1 expression and transactivation.

Significance

Glutamine-induced HSF1 expression provides a novel mechanistic frame for HSF1-Hsp axis regulation. Heat shock transcription factor-1 (HSF1) is the master regulator for cytoprotective heat shock protein (Hsp) expression. It is widely thought that HSF1 expression is non-inducible, and thus the key control point of Hsp expression is regulation of the transactivation activity of HSF1. How HSF1 expression is regulated remains unknown. Herein we demonstrate that glutamine (Gln), a preferred fuel substrate for the gut, enhanced Hsp expression both in rat colonic epithelium in vivo and in cultured non-transformed young adult mouse colonic epithelial cells. This was associated with up-regulation of the transactivation activity of HSF1 via increased HSF1 trimerization, nuclear localization, DNA binding, and relative abundance of activating phosphorylation at Ser-230 of HSF1. More intriguingly, Gln enhanced HSF1 protein and mRNA expression and Hsf1 gene promoter activity. Within the -281/-200 region of the Hsf1 promoter, deletion of the putative CCAAT enhancer-binding protein (C/EBP) binding site abolished the HSF1 response to Gln. C/EBP? was further shown to bind to this 82-bp sequence both in vitro and in vivo. Gln availability strikingly altered the ratio of C/EBP? inhibitory and active isoforms, i.e. liver-enriched inhibitory protein and liver-enriched activating protein. Liver-enriched inhibitory protein and liver-enriched activating protein were further shown to be an independent repressor and activator, respectively, for Hsf1 gene transcription, and the relative abundance of these two C/EBP? isoforms was demonstrated to determine Hsf1 transcription. We show for the first time that Gln not only enhances the transactivation of HSF1 but also induces Hsf1 expression by activating its transcription in a C/EBP?-dependent manner.

SUBMITTER: Xue H

PROVIDER: S-EPMC3504755 | biostudies-literature | 2012 Nov

REPOSITORIES: biostudies-literature

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Publications

Glutamine-mediated dual regulation of heat shock transcription factor-1 activation and expression.

Xue Hongyu H Slavov Dobromir D Wischmeyer Paul E PE

The Journal of biological chemistry 20121010 48

<h4>Background</h4>Regulation of transcriptional activity of heat shock factor-1 (HSF1) is widely thought to be the main point of control for heat shock protein (Hsp) expression.<h4>Results</h4>Glutamine increases Hsf1 gene transcription in a C/EBPβ-dependent manner and up-regulates HSF1 activity.<h4>Conclusion</h4>Glutamine is an activator for both HSF1 expression and transactivation.<h4>Significance</h4>Glutamine-induced HSF1 expression provides a novel mechanistic frame for HSF1-Hsp axis regu ...[more]

PMID: 23055521

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Project description:BackgroundThe effects of diverse stresses ultimately alter the structures and functions of proteins. As molecular chaperones, heat shock proteins (HSPs) are a group of highly conserved proteins that help in the refolding of misfolded proteins and the elimination of irreversibly damaged proteins. They are mediated by a family of transcription factors called heat shock factors (HSFs). The small abalone Haliotis diversicolor is a species naturally distributed along the southern coast of China. In this study, the expression of HdHSF1 was inhibited by RNAi in hemocytes in order to further elucidate the regulatory roles of HdHSF1 on heat shock responsive genes in abalone. Meanwhile, to understand the transcriptional regulation of the HdHSF1 gene, the 5'-upstream regulatory region of HdHSF1 was characterized, and the relative promoter activity was examined by dual-luciferase reporter gene assay system in HEK293T cell lines.ResultsAfter the inhibition of the H. diversicolor HSF1 gene (HdHSF1) by dsRNA (double-stranded RNA), the expression of most heat shock related-genes was down-regulated (p < 0.05). It indicated the importance of HdHSF1 in the heat shock response of H. diversicolor. Meanwhile, 5'-flanking region sequence (2633 bp) of the HdHSF1 gene was cloned; it contained a putative core promoter region, TATA box, CAAT box, CpG island, and many transcription elements. In HEK293T cells, the 5'-flanking region sequence can drive expression of the enhanced green fluorescent protein (EGFP), proving its promoter function. Exposure of cells to the high-temperature (39 °C and 42 °C) resulted in the activation of HdHSF1 promoter activity, which may explain why the expression of the HdHSF1 gene participates in heat shock response. Luciferase activity of different recombinant plasmids, which contained different truncated promoter fragments of the HdHSF1 gene in HEK293T cells, revealed the possible active regions of the promoter. To further identify the binding site of the critical transcription factor in the region, an expression vector with the site-directed mutation was constructed. After being mutated on the GATA-1 binding site, we found that the luciferase activity was significantly increased, which suggested that the GATA-1 binding site has a certain weakening effect on the activity of the HdHSF1 promoter.ConclusionsThese findings suggest that GATA-1 may be one of the transcription factors of HdHSF1, and a possible signaling pathway mediated by HdHSF1 may exist in H. diversicolor to counteract the adverse effects of heat shock stress.

Dataset Information

Glutamine-mediated dual regulation of heat shock transcription factor-1 activation and expression.

Background

Results

Conclusion

Significance

Publications

Glutamine-mediated dual regulation of heat shock transcription factor-1 activation and expression.

Similar Datasets

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