DISTINCT PATTERNS OF IFN SENSITIVITY OBSERVED IN CELLS INFECTED WITH VACCINIA K3L(-) AND E3L(-) MUTANT VIRUSES

Recent results have implicated a role for both the VV K3L- and E3L-enc oded gene products in conferring VV with an IFN-resistant phenotype (s eattle et al., Virology 183, 419-422, 1991; seattle et al., J. Virol. 69, 499-505, 1995). As a means of further establishing the mechanisms by which these functions mediate this process in VV-infected cells, we have further assessed the IFN phenotype in K3L(-) (vP872) and E3L(-) (vP1080) virus-infected cells. Biochemical and molecular biological an alyses were performed comparing the effects of IFN on wild-type as wel l as K3L(-) and E3L(-) virus-infected cells. Expression analyses of th e K3L and E3L gene products revealed that both are evidenced in virus- infected cells as early as 0.5 hr postinfection. E3L expression, howev er, appears more prolonged, in that it was detectable between 3 to 4 h r postinfection while K3L was undetectable after 3 hr postinfection. D espite having similar expression profiles at early times postinfection , a pronounced sensitivity of protein synthesis to IFN was observed by 30 min postinfection in VV K3L(-) virus-infected cells, whereas IFN s ensitivity was not observed in VV E3L(-)-infected cells until 2 hr pos tinfection. Subsequent analyses of the IFN-induced antiviral pathways in VV-infected cells demonstrated that the K3L gene product does not c ontribute to the previously identified specific kinase inhibitory fact or (SKIF) activity but does reduce the level of phosphorylated elF-2 a lpha in VV-infected cells. Interestingly, the IFN-induced 2',5'-oligoa denylate synthetase-mediated antiviral pathway was active in VV K3L(-) -infected cells and not in wild-type virus-infected cells. Collectivel y these results suggest that the K3L(-)- and E3L(-)-encoded products a brogate the antiviral effect of IFN at distinct levels. (C) 1995 Acade mic Press, Inc.