Heat shock transcription factor 1 is SUMOylated in the activated trimeric state.

The heat shock response is a transcriptional program of organisms to counteract an imbalance in protein homeostasis. It is orchestrated in all eukaryotic cells by heat shock transcription factor 1 (Hsf1). Despite very intensive research, the intricacies of the Hsf1 activation-attenuation cycle remain elusive at a molecular level. Post-translational modifications belong to one of the key mechanisms proposed to adapt the Hsf1 activity to the needs of individual cells, and phosphorylation of Hsf1 at multiple sites has attracted much attention. According to cell biological and proteomics data, Hsf1 is also modified by small ubiquitin-like modifier (SUMO) at several sites. How SUMOylation affects Hsf1 activity at a molecular level is still unclear. Here, we analyzed Hsf1 SUMOylation in vitro with purified components to address questions that could not be answered in cell culture models. In vitro Hsf1 is primarily conjugated at lysine 298 with a single SUMO, though we did detect low-level SUMOylation at other sites. Different SUMO E3 ligases such as protein inhibitor of activated STAT 4 enhanced the efficiency of in vitro modification but did not alter SUMO site preferences. We provide evidence that Hsf1 trimerization and phosphorylation at serines 303 and 307 increases SUMOylation efficiency, suggesting that Hsf1 is SUMOylated in its activated state. Hsf1 can be SUMOylated when DNA bound, and SUMOylation of Hsf1 does neither alter DNA-binding affinity nor affects heat shock cognate 71kDa protein (HSPA8)+DnaJ homolog subfamily B member 1-mediated monomerization of Hsf1 trimers and concomitant dislocation from DNA. We propose that SUMOylation acts at the transcription level of the heat shock response.

Comparative interactomes of HSF1 in stress and disease reveal a role for CTCF in HSF1-mediated gene regulation.

Heat shock transcription factor 1 (HSF1) orchestrates cellular stress protection by activating or repressing gene transcription in response to protein misfolding, oncogenic cell proliferation, and other environmental stresses. HSF1 is tightly regulated via intramolecular repressive interactions, post-translational modifications, and protein-protein interactions. How these HSF1 regulatory protein interactions are altered in response to acute and chronic stress is largely unknown. To elucidate the profile of HSF1 protein interactions under normal growth and chronic and acutely stressful conditions, quantitative proteomics studies identified interacting proteins in the response to heat shock or in the presence of a poly-glutamine aggregation protein cell-based model of Huntington's disease. These studies identified distinct protein interaction partners of HSF1 as well as changes in the magnitude of shared interactions as a function of each stressful condition. Several novel HSF1-interacting proteins were identified that encompass a wide variety of cellular functions, including roles in DNA repair, mRNA processing, and regulation of RNA polymerase II. One HSF1 partner, CTCF, interacted with HSF1 in a stress-inducible manner and functions in repression of specific HSF1 target genes. Understanding how HSF1 regulates gene repression is a crucial question, given the dysregulation of HSF1 target genes in both cancer and neurodegeneration. These studies expand our understanding of HSF1-mediated gene repression and provide key insights into HSF1 regulation via protein-protein interactions.

Protective role of heat shock transcription factor 1 in heart failure: A diagnostic approach.

OBJECTIVE: Nonexpression or expression inhibition of protective factors has been determined in the occurrence of heart failure (HF). Heat shock transcription factor 1 (HSF1) is among such factors, which reduces the incidence of HF by controlling cardiac hypertrophy and fibrosis. In this study, molecular mechanisms for nonexpression of HSF1 in HF patients have been investigated. MATERIALS AND METHODS: This review paper is based on the material obtained via PubMed search of 1996-2018. The key search terms were "heart failure," "heat shock transcription factor 1," "hypertrophy", "fibrosis," and "apoptosis." RESULTS: Although factors such as janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and heat shock proteins (HSPs) may respectively increase and decrease susceptibility to HF, in some circumstances, these factors may unexpectedly prevent HF progression. CONCLUSION: Finally, identification of molecular pathways expressed by various factors could be used to design appropriate treatments or to employ strategies inducing the expression of HSF1 to prevent HF.

Combined inhibition of AURKA and HSF1 suppresses proliferation and promotes apoptosis in hepatocellular carcinoma by activating endoplasmic reticulum stress.

PURPOSE: In this study we aimed to assess the anti-tumor effect of co-inhibition of Aurora kinase A (AURKA) and heat shock transcription factor 1 (HSF1) on hepatocellular carcinoma (HCC), as well as to explore the mechanism involved. METHODS: Expression of AURKA and HSF1 in primary HCC tissues and cell lines was detected by immunohistochemistry (IHC), qRT-PCR and Western blotting. AURKA was knocked down in HepG2 and BEL-7402 HCC cells using lentivirus-mediated RNA interference. Next, CCK-8, clone formation, transwell and flow cytometry assays were used to assess their viability, migration, invasion and apoptosis, respectively. The expression of proteins related to cell cycle progression, apoptosis and endoplasmic reticulum stress (ERS) was analyzed using Western blotting. In addition, in vivo tumor growth of HCC cells was assessed using a nude mouse xenograft model, and the resulting tumors were evaluated using HE staining and IHC. RESULTS: Both AURKA and HSF1 were highly expressed in HCC tissues and cells, while being negatively related to HCC prognosis. Knockdown of AURKA significantly inhibited the colony forming and migrating capacities of HCC cells. In addition, we found that treatment with an AURKA inhibitor (Danusertib) led to marked reductions in the proliferation and migration capacities of the HCC cells, and promoted their apoptosis. Notably, combined inhibition of AURKA and HSF1 induced HCC cell apoptosis, while increasing the expression of ERS-associated proteins, including p-eIF2α, ATF4 and CHOP. Finally, we found that co-inhibition of AURKA and HSF1 elicited an excellent in vivo antitumor effect in a HCC mouse model with a relatively low cytotoxicity. CONCLUSIONS: Combined inhibition of AURKA and HSF1 shows an excellent anti-tumor effect on HCC cells in vitro and in vivo, which may be mediated by ERS. These findings suggest that both AURKA and HSF1 may serve as targets for HCC treatment.

The expressions of HSFl and XAF1 in endometrial carcinoma and their correlation analysis / 西安交通大学学报(医学版)

ABSTRACT:Objective To test the expressions of heat shock transcription factor 1 (HSF1 )and XIAP-associated factor 1 (XAF1 )in different endometrial tissues,and analyze the association between their expressions and the clinicopathological features of this malignancy.Methods The expressions of HSF1 and XAF1 in 64 cases of endometria1 carcinoma (EC group)and 33 cases of normal endometrial tissues (NE group)were detected with immunohistochemistry S-P method.The correlation was observed.Results The positive expression rate of HSF1 was much higher in EC group than in NE group (76.6% vs .36.4%,P <0.05).The positive rate of XAF1 was 31.2% in EC group and 72.7% in NE group (P <0.05).The positive expressions of HSF1 and different subgroups of histological grade,myometrial invasion and lymph node metastasis were significantly different (P <0.05)in EC group.The positive expressions of XAF1 and different subgroups of histological grade,myometrial invasion,clinical stage and lymph node metastasis were significantly different (P < 0.05 )in EC group.There was a negative correlation between HSF1 and XAF1 in EC group (P <0.05).Conclusion In EC group,the high expression of HSF1 may inhibit the growth of XAF1 expression,cause excessive growth of cancer cells,reduce the apoptosis of cancer cells,and finally lead to the further development of tumors.

Regulatory fe fect of Hsf1 on PLC/PRF5 hepa toma cells proliferation / 中国免疫学杂志

Objective:To explore the regulatory effect of Hsf 1 on PLC/PRF5 hepatoma cells proliferation.Methods: By shRNA gene silencing technology ,constructed PLC/PRF5 hepatoma cell line of Hsf 1 gene silencing.To detect the expression of Hsf 1, p53 and Rb proteins in PLC/PRF5 hepatoma cells by Western blot.The proliferation of PLC/PRF5 cell line was observed by methylthiazolyl tetrazolium assay ( MTT ) , plate clone formation assay ( PCFA ) and cell cycle assay.Results: shRNA-Hsf1 could significantly inhibit the expression of Hsf 1 in PLC/PRF5 cells.It could induce PLC/PRF5 cells stopping at G1 phase of cell cycle , inhibit cell proliferation and colonal formation;silencing Hsf1 caused up-regulation of p53 and Rb proteins expression in PLC/PRF5 cells.Conclusion: Silencing Hsf1 is involved in up-regulation of p53 and Rb proteins expression , which results in inhibiting proliferation of PLC/PRF5 hepatoma cells.