RESUMEN
This study aims to construct a eukaryotic expression system for envelope gene of Jaagsiekte sheep retrovirus, observes its localization in 293T cells, and investigates the potential in inducing malignant transformation of NIH3T3 cells. By RT-PCR, the full-length cDNA of envelope gene of Jaagsiekte sheep retrovirus (exJSRV-env) was amplified from the extract of naturally infected sheep lung. The clone of target gene was sub-cloned into eukaryotic expression system pEGFP-C1, and validated by PCR, restriction endonuclease, and sequencing. Bioinformatic analysis concerning biological function and cellular localiza tion of exJSRV-env was also performed. The recombinant clone of exJSRV-env was transfected into 293T cells and NIH3T3 cells by Lipofectamine LTX. The expression and celluar localization in 293T cells were validated by confocal microscopy. Soft agar colony formation assay was employed to test the anchorage-independent growth of NIH3T3. DNA sequencing and restriction enzyme digestion with Kpn I and Hind III indicated the correct construction of the recombinant plasmid, which was named pEGFP-C1/exJSRV-env. Amino acid sequence alignment of exJSRV-env with reference sequences found 85%-100% homogeneity. A YRNM motif was discovered at the cytoplasmic tail of envelope gene, which is exclusively found in exogenous viruses. Phylogenetic tree analysis showed that our clone of exJSRV-env clustered closely with pathogenic exogenous Jaagsiekte sheep retroviruses. Fluorescence microscopy indicated typical membrane localization of exJSRV-env protein. NIH3T3 cells transfected with exJSRV-env lost contact inhibition, and acquired colony forming ability in soft agar. This study indicated that envelope protein of Jaagsiekte sheep retrovirus can induce malignant transformation of mouse fibroblast cell NIH3T3. Discoveries of this study provide a basis for further structural and functional research on Jaagsiekte sheep retrovirus envelope protein.