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Abstract

BackgroundViruses are obligate intracellular parasites and rely upon the host cell for different steps in their life cycles. The characterization of cellular genes required for virus infection and/or cell killing will be essential for understanding viral life cycles, and may provide cellular targets for new antiviral therapies.ResultsA gene entrapment approach was used to identify candidate cellular genes that affect reovirus infection or virus induced cell lysis. Four of the 111 genes disrupted in clones selected for resistance to infection by reovirus type 1 involved the insulin growth factor-2 (IGF-II) pathway, including: the mannose-6-phosphate/IGF2 receptor (Igf2r), a protease associated with insulin growth factor binding protein 5 (Prss11), and the CTCF transcriptional regulator (Ctcf). The disruption of Ctcf, which encodes a repressor of Igf2, was associated with enhanced Igf2 gene expression. Plasmids expressing either the IGF-II pro-hormone or IGF-II without the carboxy terminal extension (E)-peptide sequence independently conferred high levels of cellular resistance to reovirus infection. Forced IGF-II expression results in a block in virus disassembly. In addition, Ctcf disruption and forced Igf2 expression both enabled cells to proliferate in soft agar, a phenotype associated with malignant growth in vivo.ConclusionThese results indicate that IGF-II, and by inference other components of the IGF-II signalling pathway, can confer resistance to lytic reovirus infection. This report represents the first use of gene entrapment to identify host factors affecting virus infection. Concomitant transformation observed in some virus resistant cells illustrates a potential mechanism of carcinogenesis associated with chronic virus infection.

Role of Connexin 43 in Helicobacter pylori VacA-Induced Cell Death

“…However, the findings in the current study and several other studies indicate that gene trap selections can be used successfully in diploid or hyperdiploid cell lines (70)(71)(72)(73). We identified VacA-resistant clones with disrupted expression of Cx43 in both gene trap library and shRNA library experiments, and therefore, we analyzed the role of this host cell protein in further depth.…”

Expression of the CTCF-paralogous cancer-testis gene, brother of the regulator of imprinted sites (BORIS), is regulated by three alternative promoters modulated by CpG methylation and by CTCF and p53 transcription factors

“…We also showed that all three BORIS promoters contain CTCF-binding sites, suggesting that CTCF acts directly to regulate the BORIS promoters. The demonstration that CTCF is involved in the negative regulation of BORIS expression is likely to be important for understanding the uniform expression of BORIS in normal rat cells transformed due to a retroviral disruption of one CTCF allele ( 52 ) and in tumors of mice heterozygous for a null allele of CTCF (unpublished data).…”

Systems Biology-Based Investigation of Cellular Antiviral Drug Targets Identified by Gene-Trap Insertional Mutagenesis

“…Ebola virus (Zaire species, 1976 Mayinga strain) and Marburg virus (1967 Voege strain) were studied in a BSL4 containment facility at the Centers for Disease Control in Atlanta, GA. The U3neoSV1 retrovirus shuttle vector [ 73 ] was obtained from H. Earl Ruley (Vanderbilt University) and was used as an insertional mutagen to prepare gene-trap libraries with parental, virus-sensitive cells, as described [ 18 , 74 – 76 ].…”