IMMEDIATE-EARLY PROTEIN IE63 OF HERPES-SIMPLEX VIRUS TYPE-1 BINDS RNADIRECTLY

The herpes simplex virus type 1 (HSV-1) immediate early protein IE63 a cts post-transcriptionally to affect RNA 3'-processing and splicing. F unctional domains such as the RGG box and zinc-finger motifs potential ly provide the protein with RNA binding capacity. Here, IE63 protein e xpressed in E. coil, purified by affinity chromatography and used in R NA binding assays, demonstrated similar binding to RNA substrates cont aining poly(A) sites from different temporal classes of HSV-1 genes, R NA containing splice site recognition sequences and RNA containing no recognized processing motifs. Competition binding assays showed that I E63 binding could be competed out, suggesting that IE63 binds RNA weak ly, HSV-1 infection results in an increase or stabilization in vitro o f protein binding to poly(A) site-containing RNAs; IE63 is required fo r this effect, RNA binding assays combining purified IE63 with protein from mock-infected and HSV-1 infected nuclear extracts demonstrated n o effect on protein-RNA binding patterns.