Activation of interferon response factor-3 in human cells infected with herpes simplex virus type 1 or human cytomegalovirus.
Activation of cellular interferon-stimulated genes (ISGs) after infection with herpes simplex virus type 1 (HSV-1) or human cytomegalovirus (HCMV) was investigated. The level of ISG54-specific RNA in human fetal lung (HFL) or human foreskin (BJ) fibroblasts increased substantially after infection with either virus in the presence of cycloheximide. HSV-1 particles lacking glycoprotein D or glycoprotein H failed to induce ISG54-specific RNA synthesis, demonstrating that entry of virus particles rather than binding of virions to the cell surface was required for the effect. A DNA-binding complex that recognized an interferon-responsive sequence motif was induced upon infection with HSV-1 or HCMV in the presence of cycloheximide, and the complex was shown to contain the cell proteins interferon response factor 3 (IRF-3) and CREB-binding protein. IRF-3 was modified after infection with HSV-1 or HCMV to a form of lower electrophoretic mobility, consistent with phosphorylation. De novo transcription of viral or cellular genes was not required for the activation of IRF-3, since the effect was not sensitive to inhibition by actinomycin D. Infection of HFL fibroblasts with HSV-1 under conditions in which viral replication proceeded normally resulted in severely reduced levels of the IRF-3-containing complex, defining the activation of IRF-3 as a target for viral interference with ISG induction. In BJ fibroblasts, however, significant activation of IRF-3 was detected even when the viral gene expression program progressed to later stages, demonstrating that the degree of inhibition of the response was dependent on host cell type. As a consequence of IRF-3 activation, endogenous interferon was released from BJ cells and was capable of triggering the appropriate signal transduction pathway in both infected and uninfected cells. Activation of ISG54-specific RNA synthesis was not detected after infection of human U-373MG glioblastoma cells, showing that the induction of the response by infection is cell type dependent.
Preston
C M
CM
Medical Research Council Virology Unit, Glasgow G11 5JR, Scotland. c.preston@vir.gla.ac.uk
Harman
A N
AN
Nicholl
M J
MJ
D051017:Apoptosis Regulatory Proteins; D002460:Cell Line; D003587:Cytomegalovirus / Q000502:physiology*; D003586:Cytomegalovirus Infections / Q000378:metabolism*; D006561:Herpes Simplex / Q000378:metabolism*; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D016601:RNA-Binding Proteins; D014157:Transcription Factors / Q000378:metabolism*; D014779:Virus Replication
D051017:Apoptosis Regulatory Proteins; C484289:IFIT2 protein, human; D016601:RNA-Binding Proteins; D014157:Transcription Factors