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Heat shock proteins (HSPs), which are members of the chaperone family of proteins, are essential factors for cellular responses to environmental stressors, such as hyperthermia, and are antiapoptotic. The transcription of HSPs is mainly controlled by heat shock transcription factor 1 (HSF1). In response to environmental stress, HSF1 forms a trimer, undergoes hyperphosphorylation, and is translocated to the nucleus. In this study, we show that upon heat shock treatment of cells, a WW domain-containing propyl-isomerase, PIN1, is able to colocalize to and associate with phospho-HSF1 at Ser(326) in the nucleus via its WW domain. This interaction is required for the DNA-binding activity of HSF1 and is consistent with the lower induction of HSPs in PIN1-deficient cells. This function of PIN1 is further demonstrated by in vivo refolding and survival assays, which have shown that PIN1-deficient cells are temperature sensitive and develop apoptosis upon exposure to an environmental challenge. Moreover, the reduced levels of HSPs in PIN1-deficient cells resulted in less efficient refolding of denatured proteins. Based on our results, we propose a novel role for PIN1 whereby it acts as a stress sensor regulating HSF1 activity in response to stress on multiple levels through the transcriptional activation of stress response elements in embryonic fibroblast cells, tumor cells, and neurons.

Background: WWOX has been shown to be a candidate tumor suppressor gene in numerous human cancers. The objective of this study is to determine the expression of WWOX in human renal cell carcinoma tumor cells and its possible correlation with clinical outcome., Methods: The WWOX protein expressions of human renal cell carcinoma (RCC) tumor and of matched normal renal parenchyma were examined, and its correlation with clinical cancer-specific survival was investigated., Results: Downregulation of WWOX only in clear cell type RCC was demonstrated in our results including immunohistochemistry, Western blot, and RT-PCR assay. For the remnant cell types of RCC, sample sizes were insufficient to draw any conclusion of WWOX protein expression. The decreased expression of WWOX in clear cell RCC tumor compared with matched normal renal parenchyma was also correlated with clinical cancer-specific survival (Kaplan-Meier, p=0.0482)., Conclusions: We proved that the expression level of WWOX is downregulated in human clear cell RCC. Moreover, the decreased expression of WWOX in clear cell RCC tumor compared with matched normal renal parenchyma was also correlated with clinical cancer-specific survival. Since clear cell RCC is a special human cancer using unique molecular pathogenesis, further investigation will provide more linking intracellular signaling of WWOX and novel therapeutic targets of human renal cell carcinoma.

Human eosinophil-derived neurotoxin (EDN, RNase2) and eosinophil cationic protein (ECP, RNase3) sequences possess as high as 92% identity in their promoter regions. The major difference within this region is a 34-nucleotide (34-nt) segment appeared only in the edn promoter. In addition, six discrete segments existed in the regulatory regions of both edn and ecp. Our previous study indicated that the 34-nt segment is responsive for higher transcription activity of edn in comparison with ecp, via binding to transcription activator Sp1. In this study, the roles of the six discrete segments in transcription regulation were investigated and the -350/-329 region (ednR2) was shown to be involved in the regulation of edn expression. When the ednR2 segment of edn was replaced with that of ecp, a significant decrease in edn promoter activity was detected. Supershift, chromatin immunoprecipitation, and DNA affinity precipitation assays further showed that a transcription factor HNF4 bound to the ednR2 region of edn promoter in vitro. Interestingly, HNF4 overexpression resulted in the reduction of edn promoter activity in HepG2 cells, due to involvement of both ednR2 and the 34-nt regions, and direct interaction between HNF4 and Sp1, which abolishes Sp1 binging to the 34-nt segment. Moreover, when the Sp1 was depleted in the cell, overexpressed HNF4 enhanced edn promoter activity. Our results provide novel mechanisms for HNF4 function as an activator to regulate edn promoter activity, which account for differential transcription regulation of human eosinophil RNases.

Background: Human eosinophil-derived neurotoxin (edn) and eosinophil cationic protein (ecp) are members of a subfamily of primate ribonuclease (rnase) genes. Although they are generated by gene duplication event, distinct edn and ecp expression profile in various tissues have been reported., Results: In this study, we obtained the upstream promoter sequences of several representative primate eosinophil rnases. Bioinformatic analysis revealed the presence of a shared 34-nucleotide (nt) sequence stretch located at -81 to -48 in all edn promoters and macaque ecp promoter. Such a unique sequence motif constituted a region essential for transactivation of human edn in hepatocellular carcinoma cells. Gel electrophoretic mobility shift assay, transient transfection and scanning mutagenesis experiments allowed us to identify binding sites for two transcription factors, Myc-associated zinc finger protein (MAZ) and SV-40 protein-1 (Sp1), within the 34-nt segment. Subsequent in vitro and in vivo binding assays demonstrated a direct molecular interaction between this 34-nt region and MAZ and Sp1. Interestingly, overexpression of MAZ and Sp1 respectively repressed and enhanced edn promoter activity. The regulatory transactivation motif was mapped to the evolutionarily conserved -74/-65 region of the edn promoter, which was guanidine-rich and critical for recognition by both transcription factors., Conclusion: Our results provide the first direct evidence that MAZ and Sp1 play important roles on the transcriptional activation of the human edn promoter through specific binding to a 34-nt segment present in representative primate eosinophil rnase promoters.