COMPARATIVE ANALYSES OF THE LATENCY-ASSOCIATED TRANSCRIPT PROMOTERS FROM HERPES-SIMPLEX VIRUS TYPE-1 STRAINS H129, -63(GC AND KOS)

We have analyzed the activity of a specific portion of the latency-ass ociated transcript (LAT) promoter of three strains of herpes simplex v irus type 1 (HSV-1) in neuronal and non-neuronal cell types. Restricti on fragments containing the LAT promoter sequences and the 5'-end of t he LATs were isolated from HSV-1 strains H129, + GC and KOS-63, sequen ced and cloned into a chloramphenicol transferase (CAT) plasmid vector . These vectors were separately assayed for CAT production in human (S knSH) and mouse (C-1300) neuroblastoma cell lines and a human continuo us cell line (HeLa). Strain KOS-63 contained a C to T base substitutio n within the LAT promoter binding factor element upstream of the cAMP response element binding sequence. In replicate experiments, in which the construct DNA was used for transfection, the CAT constructs from s trains H129 and + GC functioned equally well in all three cell lines. In contrast, the strain KOS-63 CAT construct functioned significantly better in HeLa cells than in neuroblastoma cell lines and better than the identical CAT constructs from strains H129 and + GC. In addition, the construct from strain KOS-63 functioned less well in the human neu roblastoma cell line than in HeLa or C-1300 neuroblastoma cells. When LAT expression was examined directly in vivo by in situ hybridization, strain KOS-63 produced slightly less LAT RNA than strain H129 within trigeminal ganglionic neurons of latently infected rabbits. However, u tilizing competitive gel-shift assays, DNA fragments containing the LA T promoter binding element from all three strains bound equivalent amo unts of HeLa cell nuclear proteins. Together, these results suggest th at the activity expressed by the strain KOS-63 LAT promoter in vivo an d in vitro may relate to positive or negative effects of DNA binding p roteins on LAT transcription. and that these effects are cell-type dep endent. (C) 1997 Elsevier Science B.V.