Anti-DDX5 monoclonal antibody, clone 743924

Zinc-finger protein 331 (ZNF331), a Kruppel-associated box zinc-finger protein gene, was identified as a putative tumor suppressor in our previous study. However, the role of ZNF331 in tumorigenesis remains elusive. We aimed to clarify its epigenetic regulation and biological functions in gastric cancer. ZNF331 was silenced or downregulated in 71% (12/17) gastric cancer cell lines. A significant downregulation was also detected in paired gastric tumors compared with adjacent non-cancer tissues. In contrast, ZNF331 was readily expressed in various normal adult tissues. The downregulation of ZNF331 was closely linked to the promoter hypermethylation as evidenced by methylation-specific PCR, bisulfite genomic sequencing and reexpression by demethylation agent treatment. DNA sequencing showed no genetic mutation/deletion of ZNF331 in gastric cancer cell lines. Ectopic expression of ZNF331 in the silenced cancer cell lines MKN28 and HCT116 significantly reduced colony formation and cell viability, induced cell cycle arrests and repressed cell migration and invasive ability. Concordantly, knockdown of ZNF331 increased cell viability and colony formation ability of gastric cancer cell line MKN45. Two-dimensional gel electrophoresis and mass spectrometry-based comparative proteomic approach were applied to analyze the molecular basis of the biological functions of ZNF331. In all, 10 downstream targets of ZNF331 were identified to be associated with regulation of cell growth and metastasis. The tumor-suppressive effect of ZNF331 is mediated at least by downregulation of genes involved in cell growth promotion (DSTN, EIF5A, GARS, DDX5, STAM, UQCRFS1 and SET) and migration/invasion (DSTN and ACTR3), and upregulation of genome-stability gene (SSBP1) and cellular senescence gene (PNPT1). A novel target of ZNF331 (DSTN) was functionally validated. Overexpression of DSTN in BGC-823 cells increased colony formation and migration ability. In conclusion, our results suggest that ZNF331 possesses important functions for the suppression of gastric carcinogenesis as a novel functional tumor-suppressor gene. Oncogene (2013) 32, 307-317; doi:10.1038/onc.2012.54; published online 27 February 2012

To reveal the putative cellular factors involved in SARS coronavirus replication, the helicase (Hel, nsp13) of SARS coronavirus was used to screen the cDNA library of rat pulmonary epithelial cells using the yeast two-hybrid system. Positively interacting proteins were further tested using a mammalian cell hybrid system and co-immunoprecipitation in the human A549 cell line, which has been shown to support SARS coronavirus replication. Out of the seven positive clones observed by yeast two-hybrid assay, only the Ddx5 (Asp-Glu-Ala-Asp box polypeptide 5) protein showed specific interaction with SARS-CoV helicase. When expression of DdX5 was knocked down by small interfering RNA (siRNA), SARS coronavirus replication was significantly inhibited in fetal rhesus kidney (FRhK-4) cells. Since Ddx5 is a multifunctional protein that plays important roles in transcriptional regulation, its interaction with SARS coronavirus helicase provides interesting clues for studying virus-host cell interactions in SARS-CoV infections.