Functional analysis of the herpes simplex virus type 2 strain HG52 RL1 gene: the intron plays no role in virulence.

Sequence analysis predicts that herpes simplex virus type 2 (HSV-2) strain HG52 contains an open reading frame, RL1, encoding a polypeptide equivalent to ICP34.5 of HSV-1. Similarly to HSV-1, deletion of the region spanning RL1 abolishes the virulence of HSV-2 strain HG52 and its ability to grow in stationary 3T6 cells. In contrast to HSV-1, the HSV-2 strain HG52 RL1 gene is predicted to contain a 154 bp intron. Previously, we have demonstrated that this intron is spliced from RL1 poly(A)+ mRNA at the predicted splice donor/ acceptor sites. To determine if the intron affects the function of ICP34.5 of HSV-2 strain HG52, we have constructed a virus, 2624, in which the RL1 intron is deleted: 2624 retains wild-type growth both in vivo and in 3T6 cells, indicating that the presence of an intron does not affect the function of RL1 in HSV-2 strain HG52. 2624 has wild-type growth kinetics in BHK21/C13 cells.