THE PROMOTER OF THE LATENCY-ASSOCIATED TRANSCRIPTS OF HERPES-SIMPLEX VIRUS TYPE-1 CONTAINS A FUNCTIONAL CAMP-RESPONSE ELEMENT - ROLE OF THE LATENCY-ASSOCIATED TRANSCRIPTS AND CAMP IN REACTIVATION OF VIRAL LATENCY

A 203-base-pair sequence 5' of the latency-associated transcripts (LATs) of herpes simplex virus type 1 contains a 7-base consensus sequence TGCGTCA that is identical to the cAMP-response element of the proenkepahlin gene. This consensus sequence is at -38 relative to the putative 5' end of the LATs with a TAT Abox at the -24 position. In transient chloramphenicol acetyltransferase assays in rat pheochromocytoma (PC12) cells, this enhancer region stimulated gene expression up to 3-fold in the presence of dibutyryl cAMP, forskolin, nerve growth factor, or phorbol 12-myristate 13-acetate. Mutation of the cAMP-response element to TGCGCAA resulted in a 4-fold reduction of basal activity and a complete loss of inducible stimulation. In DNA gel retardation assays, purified cAMP-response element-binding protein and a nuclear protein from PC12 cells were shown to bind specifically to this element. Furthermore, it was demonstrated that the reactivation of wild-type herpes simplex virus type 1 from dissociated latently infected murine trigeminal ganglia was significantly accelerated (P < 0.005) by the addition of cAMP analogs or adenylate cyclase activators. However, these reagents did not accelerate reactivation of a deletion mutant that lacks the putative cAMP-response element-containing promoter region, transcriptional start site, and 1015 base pairs of the LATs. These studies demonstrate that the promoter region of the LATs contains a functional cAMP-response element and that expression of the LATs is likely controlled by second messenger signal transduction and imply a role for cAMP in triggering viral reactivation.