Summary. -We have previously reported that mtHSV, a herpes simplex virus 1 (HSV-1) mutant with an inactivated gene for β-galactosidase, can efficiently lyse tumor but not normal cells. However, the mechanism of this selective oncolytic activity is so far unclear. In this study, using the phage display screening we identified the cellular protein binding to HSV-1 mutant (mtHSV) as (Ras guanyl releasing protein 2) Rasgrp2 which regulates the Ras signaling pathway. Rasgrp2 was found to bind directly to purified mtHSV as well as to mtHSV present within infected HeLa cells where it aggregated on the cell membrane. NIH3T3 cells were found nonpermissive to mtHSV but they became permissive following transformation with the Rasgrp2 gene. This effect was linked to the activation of the Ras-PKR signaling pathway. These observations indicate a key role of Rasgrp2 in the mtHSV infection of NIH3T3 cells and are important for the potential use of mtHSV in cancer therapy.Keywords: herpes simplex virus 1 mutant; RAS guanyl releasing protein 2; NIH3T3 cells; permissiveness * Corresponding author. E-mail: qiyipeng@whu.edu.cn; phone: +86-27-68754131. Abbreviations: β-gal = β-galactosidase; HSV-1 = herpes simplex virus 1; MBP = maltose-binding protein; mtHSV = HSV-1 mutant; PKR = dsRNA-activated protein kinase R; Rasgrp2 = RAS guanyl releasing protein 2; siFTa = siRNA against farnesyltransferase

Genome segment 9 of bluetongue virus serotype 10 encodes the minor protein VP6. The protein is abundant with basic residues particularly in two regions of the carboxy half of the molecule. A series of amino-and carboxy-terminal deletion mutants was expressed in mammalian cells by using a vaccinia virus T7 polymerasedriven transient expression system, and the intracellular fate of the products was monitored by both immunofluorescence staining and cell fractionation techniques. Data obtained indicated clearly that VP6 has nuclear transportation signals which may be correlated with positively charged domains of the molecule. In the intact molecule, though, these signals are masked and the protein is retained in the cytoplasm. The biochemical and immunofluorescence data obtained indicate that sequences in the region of residues 33 to 80 of the 328-aminoacid protein are required for the retention of VP6 within the cell cytoplasm while amino acids 303 to 308 in the carboxy-terminal half of the molecule appear to possess nuclear localization capabilities.