ABSTRACT
The tumor necrosis factor receptor-associated factor 7 (TRAF7) is a component of the tumor necrosis factor alpha (TNF-α)/nuclear factor kappa B (NF-κB) pathway and is a putative E3-ubiquitin ligase. Based on importance of chronic inflammation in hepatocellular carcinoma (HCC), we investigated the biological effects and the molecular mechanisms of deregulated TRAF7 signaling in HCC. Our results showed that high TRAF7 expression in HCC samples was inversely associated with Krüppel-like factor 4 (KLF4) expression and the prognosis of HCC patients. TRAF7 could degrade KLF4 protein through ubiquitin by interacting with its N-terminus. The up-regulation of TRAF7 promoted HCC cell migration and invasion in vivo and in vitro, and TRAF7 knockdown had the opposite effects. Restoration of KLF4 abrogated the motility promotion induced by TRAF7. TRAF7 promotes HCC cell motility through inducing KLF4 protein turnover.
Subject(s)
Carcinoma, Hepatocellular/genetics , Kruppel-Like Transcription Factors/genetics , Liver Neoplasms/genetics , Tumor Necrosis Factor Receptor-Associated Peptides and Proteins/genetics , Adult , Animals , Carcinoma, Hepatocellular/pathology , Cell Line, Tumor , Cell Movement/genetics , Cell Proliferation/genetics , Disease Progression , Female , Gene Expression Regulation, Neoplastic/genetics , Heterografts , Humans , Kruppel-Like Factor 4 , Liver Neoplasms/pathology , Male , Mice , Middle Aged , NF-kappa B/genetics , Neoplasm Metastasis , Prognosis , Tumor Necrosis Factor-alpha/geneticsABSTRACT
Krüppel-like factor 4 (KLF4) is an important transcription factor implicated in a variety of essential cellular processes. Aberrant KLF4 expression is closely related to tumourigenesis and tumour progression. The rapid turnover of the KLF4 protein indicates an important role for the posttranslational modifications (PTMs) of KLF4. To date, E3 ligases mediating KLF4 ubiquitination have been widely reported, yet the deubiquitinating mechanism of KLF4 remains largely unknown. We screened a library of 65 deubiquitinating enzymes and identified ATXN3 as a deubiquitinating enzyme of KLF4. Subsequent immunoprecipitation assays confirmed that ATXN3 bound to KLF4, mediating the deubiquitination and stabilization of KLF4 protein levels. Furthermore, we demonstrated that ATXN3 promoted breast cancer cell metastasis via KLF4 in vitro and in vivo. Finally, the protein expression analysis of human breast cancer specimens demonstrated that ATXN3 significantly correlated with KLF4. High ATXN3/KLF4 expression was associated with a poor prognosis in breast cancer patients. Collectively, we identified ATXN3 as a novel deubiquitinating enzyme of KLF4, providing a new explanation for breast cancer metastasis, and proposed ATXN3 as a potential target for breast cancer metastasis treatment.
Subject(s)
Ataxin-3/metabolism , Breast Neoplasms/pathology , Kruppel-Like Transcription Factors/metabolism , Lung Neoplasms/pathology , Lung Neoplasms/secondary , Repressor Proteins/metabolism , Animals , Breast Neoplasms/metabolism , Cell Line, Tumor , Female , Gene Expression Regulation, Neoplastic , Humans , Kruppel-Like Factor 4 , Kruppel-Like Transcription Factors/chemistry , Lung Neoplasms/metabolism , MCF-7 Cells , Mice , Neoplasm Transplantation , Prognosis , Protein Stability , Survival Analysis , UbiquitinationABSTRACT
The addition of mono-ubiquitin or poly-ubiquitin chain to signaling proteins in response to DNA damage signal is thought to be a critical event that facilitates the recognition of DNA damage lesion site, the activation of checkpoint function, termination and checkpoint response and the recruitment of DNA repair proteins. Despite the ubiquitin modifiers, removal of ubiquitin from the functional proteins by the deubiquitinating enzymes (DUBs) plays an important role in orchestrating DNA damage response as well as DNA repair processes. Deregulated ubiquitination and deubiquitination could lead to genome instability that in turn causes tumorigenesis. Recent TCGA study has further revealed the connection between mutations in alteration of DUBs and various types of tumors. In addition, emerging drug design based on DUBs provides a new avenue for anti-cancer therapy. In this review, we will summarize the role of deubiquitination and specificity of DUBs, and highlight the recent discoveries of DUBs in the modulation of ubiquitin-mediated DNA damage response and DNA damage repair. We will furthermore discuss the DUBs involved in the tumorigenesis as well as interception of deubiquitination as a novel strategy for anti-cancer therapy.
ABSTRACT
Squamous cell differentiation requires the coordinated activation and repression of genes specific to the differentiation process; disruption of this program accompanies malignant transformation of epithelium. The exploration of genes that control epidermal proliferation and terminal differentiation is vital to better understand esophageal carcinogenesis. KLF4 is a member of the KLF family of transcription factors and is involved in both cellular proliferation and differentiation. This study using immunohistochemistry analysis of KLF4 in clinical specimens of esophageal squamous cell carcinoma (ESCC) demonstrated that decreased KLF4 was substantially associated with poor differentiation. Moreover, we determined that both KLF4 and KRT13 levels were undoubtedly augmented upon sodium butyrate-induced ESCC differentiation and G1 phase arrest. Conversely, silencing of KLF4 and KRT13 abrogated the inhibition of G1-S transition induced by sodium butyrate. Molecular investigation demonstrated that KLF4 transcriptionally regulated KRT13 and the expression of the two molecules appreciably correlated in ESCC tissues and cell lines. Collectively, these results suggest that KLF4 transcriptionally regulates KRT13 and is invovled in ESCC cell differentiation.
