Expression of the first 811 nucleotides of the herpes simplex virus type 1latency-associated transcript (LAT) partially restores wild-type spontaneous reactivation to a LAT-null mutant

The herpes simplex virus type 1 (HSV-1) latency-associated transcript (LAT) gene is required for efficient spontaneous reactivation in the rabbit ocul ar model. We recently showed that insertion of 1.8 kb of the LAT promoter a nd the first 1.5 kb of the 8.3-kb primary LAT transcript into a novel, ecto pic location in the virus unique long (UL) region restored wild-type sponta neous reactivation to a LAT-null mutant To further map the LAT spontaneous reactivation function within the first 1.5 kb of LAT, we rescued the same L AT-null mutant by inserting 1.8 kb of the LAT promoter and just the first 8 11 nucleotides of LAT into the same location in the UL. In a series of thre e experiments, the resulting virus, designated LAT2.6A, had a spontaneous r eactivation rate that was midway between the original LAT-null mutant and w ild-type virus, Thus expression of the first 811 LAT nucleotides produced a spontaneous reactivation rate that was significantly higher than that of t he LAT-null mutant but significantly less than that of wild type. This sugg ests that part but not all, of the LAT function involved in efficient spont aneous reactivation is located within the first 811 nucleotides of the prim ary 8.3-kb LAT, (C) 1999 Academic Press.