Active heat shock transcription factor 1 supports migration of the melanoma cells via vinculin down-regulation

AbstractHeat shock transcription factor 1 (HSF1), the major regulator of stress response, is frequently activated in cancer and has an apparent role in malignant transformation. Here we analyzed the influence of the over-expression of a constitutively active transcriptionally-competent HSF1 mutant form on phenotypes of mouse and human melanoma cells. We observed that the expression of active HSF1 supported anchorage-independent growth in vitro, and metastatic spread in the animal model in vivo, although the proliferation rate of cancer cells was not affected. Furthermore, active HSF1 enhanced cell motility, reduced the adherence of cells to a fibronectin-coated surface, and affected the actin cytoskeleton. We found that although the expression of active HSF1 did not affect levels of epithelial-to-mesenchymal transition markers, it caused transcriptional down-regulation of vinculin, protein involved in cell motility, and adherence. Functional HSF1-binding sites were found in mouse and human Vcl/VCL genes, indicating a direct role of HSF1 in the regulation of this gene. An apparent association between HSF1-induced down-regulation of vinculin, increased motility, and a reduced adherence of cells suggests a possible mechanism of HSF1-mediated enhancement of the metastatic potential of cancer cells

Crosstalk between HSF1 and HSF2 during the heat shock response in mouse testes

Heat Shock Factor 1 (HSF1) is the primary transcription factor responsible for the response to cellularstress, while HSF2 becomes activated during development and differentiation, including spermatogen-esis. Although both factors are indispensable for proper spermatogenesis, activation of HSF1 by heatshock initiates apoptosis of spermatogenic cells leading to infertility of males. To characterize mecha-nisms assisting such heat induced apoptosis we studied how HSF1 and HSF2 cooperate during the heatshock response. For this purpose we used chromatin immunoprecipitation and the proximity ligationapproaches. We looked for co-occupation of binding sites by HSF1 and HSF2 in untreated (32◦C) or heatshocked (at 38◦C or 43◦C) spermatocytes, which are cells the most sensitive to hyperthermia. At thephysiological temperature or after mild hyperthermia at 38◦C, the sharing of binding sites for both HSFswas observed mainly in promoters of Hsp genes and other stress-related genes. Strong hyperthermiaat 43◦C resulted in an increased binding of HSF1 and releasing of HSF2, hence co-occupation of pro-moter regions was not detected any more. The close proximity of HSF1 and HSF2 (and/or existence ofHSF1/HSF2 complexes) was frequent at the physiological temperature. Temperature elevation resultedin a decreased number of such complexes and they were barely detected after strong hyperthermia at43◦C. We have concluded that at the physiological temperature HSF1 and HSF2 cooperate in spermato-genic cells. However, temperature elevation causes remodeling of chromatin binding and interactionsbetween HSFs are disrupted. This potentially affects the regulation of stress response and contributes tothe heat sensitivity of these cells