Herpes simplex virus infection selectively stimulates accumulation of beta interferon reporter gene mRNA by a posttranscriptional mechanism.
To study the mechanism of a novel herpes simplex virus (HSV) activity that stimulates expression of reporter genes containing beta interferon (IFN-beta)-coding sequences, we have established permanent DNA-transfected cell lines that each contain two distinct hybrid genes encoding mRNA species with different half-lives. These reporter genes comprised either the human IFN-beta- or bacterial chloramphenicol acetyltransferase (CAT)-coding and 3' untranslated regions placed under the transcriptional control of the powerful major immediate-early promoter-enhancer region (IE94) from simian cytomegalovirus. Most of the dual-transfected cell lines yielded significant levels of steady-state IE94-CAT mRNA and abundant constitutive synthesis of CAT enzyme activity, whereas no accumulation of IE94-IFN mRNA could be detected. However, infection with HSV type 1 resulted in a 300-fold increase in IE94-IFN-specific mRNA transcripts, compared with no more than 3- to 5-fold stimulation of IE94-CAT-specific mRNA. In contrast, cycloheximide treatment increased stable mRNA levels and transcription initiation rates from both the IE94-IFN and IE94-CAT hybrid genes. Run-on transcription assays in isolated nuclei suggested that induction of IE94-IFN gene expression by HSV type 1 occurred predominantly at the posttranscriptional level. Enhancement of the unstable IFN mRNA species after HSV infection was also observed in cell lines containing a simian virus 40 enhancer-driven IFN gene (SV2-IFN). Similarly, in transient-transfection assays, both SV2-IFN and IE94-IFN gave only low basal mRNA synthesis, but superinfection with HSV again led to high-level accumulation of IFN mRNA. Finally, substitution of the SV2-IFN gene 3' region with poly(A) and splicing signals from the SV2-CAT gene cassette led to stabilization of the IFN mRNA even in the absence of HSV. Therefore, we conclude that HSV infection leads to selective accumulation of IFN-beta mRNA by a posttranscriptional mechanism that is reporter gene specific and promoter independent.
Mosca
J D
JD
Oncology Center, Johns Hopkins School of Medicine, Baltimore, Maryland 21205.
Pitha
P M
PM
Hayward
G S
GS
D015500:Chloramphenicol O-Acetyltransferase / Q000096:biosynthesis / Q000235:genetics; D003513:Cycloheximide / Q000494:pharmacology; D003587:Cytomegalovirus / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics; D006207:Half-Life; D006561:Herpes Simplex / Q000378:metabolism*; D006801:Humans; D016899:Interferon-beta / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D009693:Nucleic Acid Hybridization; D015347:RNA Probes; D012333:RNA, Messenger / Q000378:metabolism*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D018139:Simplexvirus / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection; D014170:Transformation, Genetic
D004274:DNA, Recombinant; D015347:RNA Probes; D012333:RNA, Messenger; D016899:Interferon-beta; D003513:Cycloheximide; D015500:Chloramphenicol O-Acetyltransferase