BackgroundJapanese encephalitis virus (JEV) infection is a major cause of acute encephalopathy in children, which destroys central nervous system (CNS) cells, including astrocytes and neurons. Matrix metalloproteinase (MMP)-9 has been shown to degrade components of the basal lamina, leading to disruption of the blood-brain barrier (BBB) and to contribute to neuroinflammatory responses in many neurological diseases. However, the detailed mechanisms of JEV-induced MMP-9 expression in rat brain astrocytes (RBA-1 cells) are largely unclear.MethodsIn this study, the effect of JEV on expression of MMP-9 was determined by gelatin zymography, western blot analysis, RT-PCR, and promoter assay. The involvement of AP-1 (c-Jun and c-Fos), c-Src, PDGFR, PI3K/Akt, and MAPKs in these responses were investigated by using the selective pharmacological inhibitors and transfection with siRNAs.ResultsHere, we demonstrate that JEV induces expression of pro-form MMP-9 via ROS/c-Src/PDGFR/PI3K/Akt/MAPKs-dependent, AP-1 activation in RBA-1 cells. JEV-induced MMP-9 expression and promoter activity were inhibited by pretreatment with inhibitors of AP-1 (tanshinone), c-Src (PP1), PDGFR (AG1296), and PI3K (LY294002), and by transfection with siRNAs of c-Jun, c-Fos, PDGFR, and Akt. Moreover, JEV-stimulated AP-1 activation was inhibited by pretreatment with the inhibitors of c-Src, PDGFR, PI3K, and MAPKs.ConclusionFrom these results, we conclude that JEV activates the ROS/c-Src/PDGFR/PI3K/Akt/MAPKs pathway, which in turn triggers AP-1 activation and ultimately induces MMP-9 expression in RBA-1 cells. These findings concerning JEV-induced MMP-9 expression in RBA-1 cells imply that JEV might play an important role in CNS inflammation and diseases.

Oncogenic activation of the Wnt/b-catenin signaling pathway is common in hepatocellular carcinoma (HCC). Our recent studies have demonstrated that SRY (sex determining region Y)-box 1 (SOX1) and secreted frizzled-related proteins are concomitantly promoter-hypermethylated, and this might lead to abnormal activation of the Wnt signaling pathway in HCC. SOX1 encodes a transcription factor involved in the regulation of embryonic development and cell fate determination. However, the expression and functional role of SOX1 in HCC remains unclear. In this study, we confirmed via quantitative methylation-specific polymerase chain reaction that SOX1 was frequently downregulated through promoter hypermethylation in HCC cells and tissues. Overexpression of SOX1 by a constitutive or inducible approach could suppress cell proliferation, colony formation, and invasion ability in HCC cell lines, as well as tumor growth in nonobese diabetic/severe combined immunodeficiency mice. Conversely, knockdown of SOX1 by withdrawal of doxycycline could partially restore cell proliferation and colony formation in HCC cells. We used a T cell factor (TCF)-responsive luciferase reporter assay and western blot analysis to prove that SOX1 could regulate TCF-responsive transcriptional activity and inhibit the expression of Wnt downstream genes. Furthermore, we used glutathione S-transferase pull-down, co-immunoprecipitation, and confocal microscopy to demonstrate that SOX1 could interact with b-catenin but not with the b-catenin/TCF complex. Moreover, restoration of the expression of SOX1 induces significant cellular senescence in Hep3B cells. Conclusion: Our data show that a developmental gene, SOX1, may function as a tumor suppressor by interfering with Wnt/b-catenin signaling in the development of HCC. (HEPATOLOGY 2012;56:2277-2287 T he incidence and mortality of hepatocellular carcinoma (HCC) have been increasing rapidly worldwide in recent decades.1 The risk factors associated with hepatocarcinogenesis are numerous and include chronic hepatitis B or C viral infection, alcohol, aflatoxin B1, and others. However, the molecular mechanisms involved in the development of HCC remain unclear. Recent studies have demonstrated that inactivation of tumor suppressor genes (TSGs) through promoter hypermethylation plays an essential role in carcinogenesis.2,3 Furthermore, methylation profiles have been used as potential biomarkers for early diagnosis, prognostic prediction, and screening in HCC. 4 Therefore, exploring the molecular mechanisms of the inactivation of TSGs involved in HCC development could improve the treatment of HCC in the future.

During recent studies of ribonucleolytic ''degradosome'' complexes of Escherichia coli, we found that degradosomes contain certain RNAs as well as RNase E and other protein components. One of these RNAs is ssrA (for small stable RNA) RNA (also known as tm RNA or 10Sa RNA), which functions as both a tRNA and mRNA to tag the C-terminal ends of truncated proteins with a short peptide and target them for degradation. Here, we show that mature 363-nt ssrA RNA is generated by RNase E cleavage at the CCA-3 terminus of a 457-nt ssrA RNA precursor and that interference with this cleavage in vivo leads to accumulation of the precursor and blockage of SsrA-mediated proteolysis. These results demonstrate that RNase E is required to produce mature ssrA RNA and for normal ssrA RNA peptide-tagging activity. Our findings indicate that RNase E, an enzyme already known to have a central role in RNA processing and decay in E. coli, also has the previously unsuspected ability to affect protein degradation through its role in maturation of the 3 end of ssrA RNA. R ibonuclease E (RNase E), which is essential for cell growth and was initially characterized as the enzyme that processes 9S RNA to yield a 5S product, p5S RNA (1), has been shown to control the rate-limiting step in the degradation of a variety of Escherichia coli mRNAs (for reviews, see refs. 2-5), and a small regulatory RNA, RNAI-an antisense repressor of the replication primer of ColE1-type plasmids (6 -8). Temperaturesensitive mutants of RNase E have been isolated (9-12) and mapped to its enzymatic active domain (13), which is located at the N-terminal half of the polypeptide (14, 15). Inactivation of RNase E activity in these mutants by culture at nonpermissive temperature prolongs the decay of bulk mRNA (11,12).Recently, an RNase E-containing multicomponent ribonucleolytic complex termed the ''RNA degradosome'' has been isolated and characterized by two distinct approaches (16, 17), both of which show that degradosomes contain the protein components RNase E, PNPase, RhlB RNA helicase, and enolase. In addition to these proteins, the degradosome was found to contain the chaperonins DnaK (16, 18) and GroEL (16), polyphosphate kinase (18), mRNA, and certain structural RNA species (16,19), including RNAI, fragmented rRNAs, 9S RNA, and 10Sa͞ssrA RNA [a small stable RNA encoded by the ssrA gene (20)(21)(22)]. Most of these RNAs are known to be substrates for RNase E (19,[23][24][25][26].Nascent polypeptides translated in E. coli from truncated mRNAs lacking stop codons commonly receive a short carboxylterminal peptide tag (27, 28), synthesized in trans (28,29), that targets the resulting fusion polypeptide for rapid degradation (28). Except for the first alanine, the amino acid sequence of this tag (AANDENYALAA) is encoded by 10Sa͞ssrA RNA (20)(21)(22), also known as tmRNA because of its dual tRNA-like and mRNA-like activities (22,(28)(29)(30). Mature 363-nt ssrA RNA, which has its 3Ј and 5Ј ends paired in a tRNA-like structure, is charged with an alanine residue (22, 30), ...

The promyelocytic leukaemia (PML) protein controls multiple tumour suppressive functions and is downregulated in diverse types of human cancers through incompletely characterized post-translational mechanisms. Here we identify USP11 as a PML regulator by RNAi screening. USP11 deubiquitinates and stabilizes PML, thereby counteracting the functions of PML ubiquitin ligases RNF4 and the KLHL20–Cul3 (Cullin 3)–Roc1 complex. We find that USP11 is transcriptionally repressed through a Notch/Hey1-dependent mechanism, leading to PML destabilization. In human glioma, Hey1 upregulation correlates with USP11 and PML downregulation and with high-grade malignancy. The Notch/Hey1-induced downregulation of USP11 and PML not only confers multiple malignant characteristics of aggressive glioma, including proliferation, invasiveness and tumour growth in an orthotopic mouse model, but also potentiates self-renewal, tumour-forming capacity and therapeutic resistance of patient-derived glioma-initiating cells. Our study uncovers a PML degradation mechanism through Notch/Hey1-induced repression of the PML deubiquitinase USP11 and suggests an important role for this pathway in brain tumour pathogenesis.