Helicase-like transcription factor (HLTF) has been found to be involved in the maintenance of genome stability and tumoursuppression, but whether its downregulation in cancers is associated with posttranslational regu...Helicase-like transcription factor (HLTF) has been found to be involved in the maintenance of genome stability and tumoursuppression, but whether its downregulation in cancers is associated with posttranslational regulation remains unclear. Here, weobserved that HLTF was significantly downregulated in hepatocellular carcinoma (HCC) tissues and positively associated with thesurvival of HCC patients. Mechanistically, the decreased expression of HLTF in HCC was attributed to elevated β-TrCP-mediated ubiquitination and degradation. Knockdown of HLTF enhanced p62 transcriptional activity and mammalian target of rapamycin (mTOR)activation, leading to HCC tumourigenesis. Inhibition of mTOR effectively blocked β-TrCP overexpression- or HLTF knockdownmediated HCC tumourigenesis and metastasis. Furthermore, in clinical tissues, decreased HLTF expression was positively correlatedwith elevated expression of β-TrCP, p62, or p-mTOR in HCC patients. Overall, our data not only uncover new roles of HLTF in HCCcell proliferation and metastasis, but also reveal a novel posttranslational modification of HLTF by β-TrCP, indicating that theβ-TrCP/HLTF/p62/mTOR axis may be a new oncogenic driver involved in HCC development. This finding provides a potentialtherapeutic strategy for HCC patients by targeting the β-TrCP/HLTF/p62/mTOR axis.展开更多
Many biological processes such as cell proliferation, differentiation, and cell death depend precisely on the timely synthesis and degradation of key regulatory proteins. While protein synthesis can be regulated at mu...Many biological processes such as cell proliferation, differentiation, and cell death depend precisely on the timely synthesis and degradation of key regulatory proteins. While protein synthesis can be regulated at multiple levels, protein degradation is mainly controlled by the ubiquitin-proteasome system （UPS）, which consists of two distinct steps： （1） ubiquitylation of targeted protein by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin ligase, and （2） subsequent degradation by the 26S proteasome. Among all E3 ubiquitin ligases, the SCF （SKP1-CUL1-F-box protein） E3 ligases are the largest family and are responsible for the turnover of many key regulatory proteins. Aberrant regulation of SCF E3 ligases is associated with various human diseases, such as cancers, including skin cancer. In this review, we provide a comprehensive overview of all currently published data to define a promoting role of SCF E3 ligases in the development of skin cancer. The future directions in this area of research are also discussed with an ultimate goal to develop small molecule inhibitors of SCF E3 ligases as a novel approach for the treatment of human skin cancer. Furthermore, altered components or substrates of SCF E3 ligases may also be developed as the biomarkers for early diagnosis or predicting prognosis.展开更多
基金supported by the Introduction of Special Funds for Talents from the Third Military Medical University(Army Medical University,4174C6)to C.-M.X.
文摘Helicase-like transcription factor (HLTF) has been found to be involved in the maintenance of genome stability and tumoursuppression, but whether its downregulation in cancers is associated with posttranslational regulation remains unclear. Here, weobserved that HLTF was significantly downregulated in hepatocellular carcinoma (HCC) tissues and positively associated with thesurvival of HCC patients. Mechanistically, the decreased expression of HLTF in HCC was attributed to elevated β-TrCP-mediated ubiquitination and degradation. Knockdown of HLTF enhanced p62 transcriptional activity and mammalian target of rapamycin (mTOR)activation, leading to HCC tumourigenesis. Inhibition of mTOR effectively blocked β-TrCP overexpression- or HLTF knockdownmediated HCC tumourigenesis and metastasis. Furthermore, in clinical tissues, decreased HLTF expression was positively correlatedwith elevated expression of β-TrCP, p62, or p-mTOR in HCC patients. Overall, our data not only uncover new roles of HLTF in HCCcell proliferation and metastasis, but also reveal a novel posttranslational modification of HLTF by β-TrCP, indicating that theβ-TrCP/HLTF/p62/mTOR axis may be a new oncogenic driver involved in HCC development. This finding provides a potentialtherapeutic strategy for HCC patients by targeting the β-TrCP/HLTF/p62/mTOR axis.
基金supported by the National Cancer Institute grants (Nos. CA118762, CA156744, CA170995 and CA171277) to Y.Sthe National Institute of General Medical Sciences grant (No. GM094777) to W.W
文摘Many biological processes such as cell proliferation, differentiation, and cell death depend precisely on the timely synthesis and degradation of key regulatory proteins. While protein synthesis can be regulated at multiple levels, protein degradation is mainly controlled by the ubiquitin-proteasome system （UPS）, which consists of two distinct steps： （1） ubiquitylation of targeted protein by E1 ubiquitin-activating enzyme, E2 ubiquitin-conjugating enzyme and E3 ubiquitin ligase, and （2） subsequent degradation by the 26S proteasome. Among all E3 ubiquitin ligases, the SCF （SKP1-CUL1-F-box protein） E3 ligases are the largest family and are responsible for the turnover of many key regulatory proteins. Aberrant regulation of SCF E3 ligases is associated with various human diseases, such as cancers, including skin cancer. In this review, we provide a comprehensive overview of all currently published data to define a promoting role of SCF E3 ligases in the development of skin cancer. The future directions in this area of research are also discussed with an ultimate goal to develop small molecule inhibitors of SCF E3 ligases as a novel approach for the treatment of human skin cancer. Furthermore, altered components or substrates of SCF E3 ligases may also be developed as the biomarkers for early diagnosis or predicting prognosis.
