Activation of cellular promoters during herpes virus infection of biochemically transformed cells.

At least two of the immediate-early (IE) products of herpes simplex virus-1 (HSV-1) are responsible for the activation of transcription from viral early promoters. This process appears not to be promoter specific since several unrelated viral and cellular plasmid-borne promoters can also be activated in short-term transfection assays. This paper describes experiments that show that cellular promoters integrated into the host genome can also be activated during viral infection, and that this process is brought about by IE gene products. Biochemically transformed cell lines were isolated following transfection of plasmids containing the human epsilon-globin promoter linked to the herpes thymidine kinase coding region (as selectable marker), and an unselected rabbit beta-globin gene. Infection of some, but not all, such cell lines with HSV-1 resulted in a rapid and considerable stimulation of the integrated epsilon- and beta-globin promoters. Both promoters could also be activated (albeit less efficiently) during pseudorabies virus infection, and after introduction by transfection of plasmids containing HSV IE genes. The implications of these results for viral-host interactions and the mechanism of viral-induced promoter activation are discussed.