Temporal regulation of herpes simplex virus type 1 transcription: location of transcripts on the viral genome

Abstract

Nuclear and cytoplasmic viral RNAs, synthesized in cells productively infected with herpes simplex virus type 1 at early and late times post-infection and in the presence of DNA and protein synthesis inhibitors, have been analyzed by blot hybridization to viral DNA fragments generated by single and double digests with the Hind III, Bgl II and Hpa I restriction endonucleases. RNA transcribed in the presence of cycloheximide (immediate early, made using a cell RNA polymerase) hybridizes to restricted portions of the HSV-1 genome, and the hybridization patterns of both nuclear and cytoplasmic immediate early RNAs are similar. This finding suggests that synthesis of immediate early RNA within the nucleus may be restricted; alternatively, there may be rapid processing of primary transcripts. Virus-induced protein synthesis is a prerequisite for the switch from the restricted immediate early to the early pattern of transcription in which there is hybridization to all the DNA fragments. The hybridization pattern of RNA labeled in the presence of cytosine arabinoside resembles that of early RNA. Late RNA also hybridizes to all the DNA fragments, but the relative hybridization to the individual DNA fragments is different between early and late times. When late nuclear and late cytoplasmic RNAs are compared, there is greater relative hybridization to several different regions of the genome with nuclear RNA. This implies that either translocation of transcripts to the cytoplasm is regulated or that certain RNAs are degraded more rapidly within the cytoplasm.