Heat shock factor 1 (Hsf1) cooperates with estrogen receptor α (erα) in the regulation of estrogen action in breast cancer cells

Heat shock factor 1 (HSF1), a key regulator of transcriptional responses to proteotoxic stress, was linked to estrogen (E2) signaling through estrogen receptor α (ERα). We found that an HSF1 deficiency may decrease ERα level, attenuate the mitogenic action of E2, counteract E2-stimulated cell scattering, and reduce adhesion to collagens and cell motility in ER-positive breast cancer cells. The stimulatory effect of E2 on the transcriptome is largely weaker in HSF1-deficient cells, in part due to the higher basal expression of E2-dependent genes, which correlates with the enhanced binding of unliganded ERα to chromatin in such cells. HSF1 and ERα can cooperate directly in E2-stimulated regulation of transcription, and HSF1 potentiates the action of ERα through a mechanism involving chromatin reorganization. Furthermore, HSF1 deficiency may increase the sensitivity to hormonal therapy (4-hydroxytamoxifen) or CDK4/6 inhibitors (palbociclib). Analyses of data from The Cancer Genome Atlas database indicate that HSF1 increases the transcriptome disparity in ER-positive breast cancer and can enhance the genomic action of ERα. Moreover, only in ER-positive cancers an elevated HSF1 level is associated with metastatic disease.publishedVersio

Location of promoter elements necessary and sufficient to direct testis-specific expression of the Hst70/Hsp70.2 gene.

The rat Hst70 gene and its mouse counterpart Hsp70.2 are expressed specifically in pachytene primary spermatocytes and spermatids. Here we demonstrate that a 165 bp fragment of the Hst70 gene promoter, containing the T1 transcription start site region, entire exon 1 and 42 bp 5' region of the intron, is sufficient to drive testis-specific expression of the chloramphenicol acetyltransferase reporter gene in transgenic mice with the same developmentally regulated pattern as the endogenous Hsp70.2 gene. We show further that high-level tissue-specific gene expression requires additional sequences localized upstream of the T2 transcription start site. Electrophoretic mobility-shift assay analysis revealed that only testes of juvenile rats, when Hst70 gene expression is repressed, contain proteins that specifically bind to the Oct (octamer) sequence localized directly downstream of the T1 site

The activity of acid phosphatase and the level of storage proteins during the early stages of germination of Lupinus luteus L. and Lupinus angustifolius L. seeds

Changes in the level of protein and in the activity of acid phosphatase in seeds of Lupinus luteus L. and Lupinus angustifolius L. during storage and germination were studied. The protein level decreased during germination, mainly as the result of a fall in the concentration of β-conglutin. After an initial decrease in the activity of acid phosphatase activity during the first five days of germination, the activity of this enzyme began to rise with the appearance of two new molecular forms. No significant effect of gibberelin A3 on the specific ativity of acid phosphatase was observed

PHLDA1 Does Not Contribute Directly to Heat Shock-Induced Apoptosis of Spermatocytes

Spermatocytes are among the most heat-sensitive cells and the exposure of testes to heat shock results in their Heat Shock Factor 1 (HSF1)-mediated apoptosis. Several lines of evidence suggest that pleckstrin-homology-like domain family A, member 1 (PHLDA1) plays a role in promoting heat shock-induced cell death in spermatogenic cells, yet its precise physiological role is not well understood. Aiming to elucidate the hypothetical role of PHLDA1 in HSF1-mediated apoptosis of spermatogenic cells we characterized its expression in mouse testes during normal development and after heat shock. We stated that transcription of Phlda1 is upregulated by heat shock in many adult mouse organs including the testes. Analyzes of the Phlda1 expression during postnatal development indicate that it is expressed in pre-meiotic or somatic cells of the testis. It starts to be transcribed much earlier than spermatocytes are fully developed and its transcripts and protein products do not accumulate further in the later stages. Moreover, neither heat shock nor expression of constitutively active HSF1 results in the accumulation of PHLDA1 protein in meiotic and post-meiotic cells although both conditions induce massive apoptosis of spermatocytes. Furthermore, the overexpression of PHLDA1 in NIH3T3 cells leads to cell detachment, yet classical apoptosis is not observed. Therefore, our findings indicate that PHLDA1 cannot directly contribute to the heat-induced apoptosis of spermatocytes. Instead, PHLDA1 could hypothetically participate in death of spermatocytes indirectly via activation of changes in the somatic or pre-meiotic cells present in the testes

The GC-box is critical for high level expression of the testis-specific Hsp70.2/Hst70 gene

The Hsp70.2/Hst70 gene, which belongs to the 70 kDa heat-shock protein (HSP) family, is expressed specifically in primary spermatocytes and spermatids. The regulatory elements required for a high level of testis-specific expression of the gene are placed between the two major transcription start sites T1 and T2 (approximately 350 and 115 bp upstream of the starting ATG codon). Here we have shown that sequences proximal to the exon1/intron splicing site in the 5' untranslated region of the Hsp70.2/Hst70 gene, which include a highly conserved element called box B, are required for efficient expression of the chloramphenicol acetyltransferase reporter gene in testes of transgenic mice. However, in spite of the drastically reduced overall activity, the stage-specific expression pattern of the transgene was preserved after removal of these sequences. We have also shown that GC-box located downstream of the box B (approximately 210 bp upstream of the starting ATG codon) is indispensable for efficient expression of the Hsp70.2/Hst70 gene promoter in spermatogenic cells. The GC-box specifically binds proteins present in nuclear extracts from testes (putatively Sp1-like factors). A change in the pattern of such GC-box-interacting factors corresponds to activation of the Hsp70.2/Hst70 gene, confirming the importance of this regulatory element

Expression of a constitutively active mutant of heat shock factor 1 under the control of testis-specific hst70 gene promoter in transgenic mice induces degeneration of seminiferous epithelium.

Heat shock activates in somatic cells a set of genes encoding heat shock proteins which function as molecular chaperones. The basic mechanism by which these genes are activated is the interaction of the specific transcription factor HSF1 with a regulatory DNA sequence called heat shock element (HSE). In higher eukaryotes HSF1 is present in unstressed cells as inactive monomers which, in response to cellular stress, aggregate into transcriptionally competent homotrimers. In the present paper we showed that the expression of a transgene encoding mutated constitutively active HSF1 placed under the control of a spermatocyte-specific promoter derived from the hst70 gene severely affects spermatogenesis. We found the testes of transgenic mice to be significantly smaller than those of wild-type males and histological analysis showed massive degeneration of the seminiferous epithelium. The lumen of tubules was devoid of spermatids and spermatozoa and using the TUNEL method we demonstrated a high rate of spermatocyte apoptosis. The molecular mechanism by which constitutively active HSF1 arrests spermatogenesis is not known so far. One can assume that HSF1 can either induce or repress so far unknown target genes involved in germ cell apoptosis