Abstract
Abstract: :
Purpose: Previous studies have identified predicted YY1 binding sites in the first intron of the HSV–1 ICP0 gene. Since YY1 is abundantly expressed in primary sensory neurons of the trigeminal ganglion (TG), and ICP0 is critical for efficient HSV–1 productive infection, we set out to determine whether YY1 plays an inhibitory role in both ICP0 gene expression and productive HSV–1 infection. Methods: Dual immunofluorescence was performed with YY1 specific antisera as well as monoclonal Abs KH10 and A5 which identify TG neuronal populations with greater and lesser permissiveness for HSV–1 productive infection, respectively. The YY1 cell line was established by transfection with a YY1–expression plasmid and selection with G418. Single and multi–step viral growth curves were carried out using standard plaque assays. Priscilla Schaffer provided us with the HSV–1 ICP0 null mutant. Transient assays were performed by flow cytometry and luciferase assay. Specific binding of YY1 to the ICP0 gene was evaluated by electrophoretic mobility shift assay (EMSA). Results: Array analysis of murine cDNA from A5 and KH10 neurons suggested signficiantly greater YY1 expression in A5 neurons than KH10 neurons. Immunofluorescent staining of murine TG confirmed greater YY1 expression in A5 neurons than in KH10 neurons. Wildtype HSV–1 (KOS) grew less well in the YY1 expressing cell line than in control lines. In contrast, the ICP0 null mutant (lacking YY1 binding sites) grew equally well in YY1–expressing cells as in a controls. In transient assays, YY1 repressed ICP0 promoter activity, but not ICP4 promoter activity. Finally, as assayed by EMSA, YY1 exhibited specific binding to the first intron, but not the promoter, of the ICP0 gene. YY1 antisera competitively inhibited this binding. Conclusions: YY1, a transcription factor expressed in TG neurons, appears to act on intron–1 of the ICP0 gene to repress productive HSV–1 infection. This may be one reason why these neurons are relatively non–permissive for productive HSV–1 infection.
Keywords: herpes simplex virus • transcription factors