Carboxyl terminus of Hsp70-interacting protein (CHIP) contributes to human glioma oncogenesis.
ABSTRACT Malignant glioma is the most common adult primary brain tumor, and the mechanism of its oncogenesis is poorly understood. Growing evidence has shown that E3 ubiquitin ligases can promote tumorgenesis of glioma. CHIP is an E3 ubiquitin ligase that can induce ubiquitylation and degradation of many tumor-related proteins, and it has been reported to act as an upstream regulator in breast cancer; however, its role in human gliomas has not been evaluated yet. In this study, the expression of CHIP in glioma tissues was studied using immunohistochemistry. CHIP expression in glioma cells was studied by real-time RT-PCR, western blot and double immunofluorescence staining. The role of CHIP in glioma oncogenesis was investigated by lentivirus-mediated RNA interference (RNAi) and overexpression in vitro and in vivo. We showed CHIP expression in glioma samples was related to tumor grades, with stronger staining in high-grade gliomas than in low-grade gliomas. Knocking down of CHIP suppressed proliferation, colony formation of U251 and U87 glioma cells, while overexpression of CHIP resulted in enhanced proliferation and colony formation in vitro. In a nude mouse xenograft model, intratumoral injection of CHIP RNAi lentivirus significantly delayed tumor growth. In contrast, overexpression of CHIP resulted in enhanced tumor growth in vivo. After CHIP RNAi, both survivin mRNA and protein were decreased, while CHIP overexpression induced increased mRNA and protein levels of survivin. This is the first study demonstrating CHIP contributes to oncogenesis of glioma.
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ABSTRACT: The p53 tumour-suppressor protein exerts antiproliferative effects, including growth arrest and apoptosis, in response to various types of stress. The activity of p53 is abrogated by mutations that occur frequently in tumours, as well as by several viral and cellular proteins. The Mdm2 oncoprotein is a potent inhibitor of p53. Mdm2 binds the transcriptional activation domain of p53 and blocks its ability to regulate target genes and to exert antiproliferative effects. On the other hand, p53 activates the expression of the mdm2 gene in an autoregulatory feedback loop. The interval between p53 activation and consequent Mdm2 accumulation defines a time window during which p53 exerts its effects. We now report that Mdm2 also promotes the rapid degradation of p53 under conditions in which p53 is otherwise stabilized. This effect of Mdm2 requires binding of p53; moreover, a small domain of p53, encompassing the Mdm2-binding site, confers Mdm2-dependent detstabilization upon heterologous proteins. Raised amounts of Mdm2 strongly repress mutant p53 accumulation in tumour-derived cells. During recovery from DNA damage, maximal Mdm2 induction coincides with rapid p53 loss. We propose that the Mdm2-promoted degradation of p53 provides a new mechanism to ensure effective termination of the p53 signal.Nature 06/1997; 387(6630):296-9. · 38.60 Impact Factor
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ABSTRACT: The chaperone function of the mammalian 70-kDa heat shock proteins Hsc70 and Hsp70 is modulated by physical interactions with four previously identified chaperone cofactors: Hsp40, BAG-1, the Hsc70-interacting protein Hip, and the Hsc70-Hsp90-organizing protein Hop. Hip and Hop interact with Hsc70 via a tetratricopeptide repeat domain. In a search for additional tetratricopeptide repeat-containing proteins, we have identified a novel 35-kDa cytoplasmic protein, carboxyl terminus of Hsc70-interacting protein (CHIP). CHIP is highly expressed in adult striated muscle in vivo and is expressed broadly in vitro in tissue culture. Hsc70 and Hsp70 were identified as potential interaction partners for this protein in a yeast two-hybrid screen. In vitro binding assays demonstrated direct interactions between CHIP and both Hsc70 and Hsp70, and complexes containing CHIP and Hsc70 were identified in immunoprecipitates of human skeletal muscle cells in vivo. Using glutathione S-transferase fusions, we found that CHIP interacted with the carboxy-terminal residues 540 to 650 of Hsc70, whereas Hsc70 interacted with the amino-terminal residues 1 to 197 (containing the tetratricopeptide domain and an adjacent charged domain) of CHIP. Recombinant CHIP inhibited Hsp40-stimulated ATPase activity of Hsc70 and Hsp70, suggesting that CHIP blocks the forward reaction of the Hsc70-Hsp70 substrate-binding cycle. Consistent with this observation, both luciferase refolding and substrate binding in the presence of Hsp40 and Hsp70 were inhibited by CHIP. Taken together, these results indicate that CHIP decreases net ATPase activity and reduces chaperone efficiency, and they implicate CHIP in the negative regulation of the forward reaction of the Hsc70-Hsp70 substrate-binding cycle.Molecular and Cellular Biology 07/1999; 19(6):4535-45. · 5.37 Impact Factor
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ABSTRACT: To investigate the risks of mortality and cancer incidence in Parkinson's disease (PD) we studied the prognosis of 246 PD patients in a community. The cohort of PD patients was identified in 1984, and survival, mortality, relocation, and cancer incidence during 1984-1992 were examined retrospectively in 1994. The risk was measured by a standard effect estimate, i.e., the standardized mortality ratio (SMR) or the standardized incidence ratio (SIR), compared with the rates in the general population. During the observation period 696 person-years in PD men and 1018 person-years in PD women were accumulated, and 49 PD men and 53 PD women died. The risk of mortality in PD was significantly increased in both sexes (SMR: men 1.74, women 1.97). In addition, the risk of cancer incidence was evaluated in 228 patients aged under 80 years; 8 PD men and 7 PD women developed cancer. The risk of overall cancer incidence in PD was less than 1 in either sex, but not significantly. The risk of breast cancer in PD women was significantly increased (SIR: 5.49), but the 95% confidence interval was wide (1.10-16.03). The results indicate that PD patients in a community have a twofold higher risk of mortality, and that PD may be associated with an increased risk of breast cancer in women.Journal of Neurology 07/2000; 247(6):429-34. · 3.58 Impact Factor