Cell lines that support replication of a novel herpes simplex virus 1 U L31 deletion mutant can properly target U L34 protein to the nuclear rim in the absence of U L31

Abstract

Previous results indicated that the herpes simplex virus 1 (HSV-1) U L31 gene is necessary and sufficient for localization of the U L34 protein exclusively to the nuclear membrane of infected Hep2 cells. In the current studies, a bacterial artificial chromosome containing the entire HSV-1 strain F genome was used to construct a recombinant viral genome in which a gene encoding kanamycin resistance was inserted in place of 262 codons of the 306 codon U L31 open reading frame. The deletion virus produced virus titers approximately 10- to 50-fold lower in rabbit skin cells, more than 2000-fold lower in Vero cells, and more than 1500-fold lower in CV1 cells, compared to a virus bearing a restored U L31 gene. The replication of the U L31 deletion virus was restored on U L31-complementing cell lines derived either from rabbit skin cells or CV1 cells. Confocal microscopy indicated that the majority of U L34 protein localized aberrantly in the cytoplasm and nucleoplasm of Vero cells and CV1 cells, whereas U L34 protein localized at the nuclear membrane in rabbit skin cells, and U L31 complementing CV1 cells infected with the U L31 deletion virus. We conclude that rabbit skin cells encode a function that allows proper localization of U L34 protein to the nuclear membrane. We speculate that this function partially complements that of U L31 and may explain why U L31 is less critical for replication in rabbit skin cells as opposed to Vero and CV1 cells.