Tpl2/AP-1 enhances murine gammaherpesvirus 68 lytic replication.
How cellular factors regulate gammaherpesvirus lytic replication is not well understood. Here, through functional screening of a cellular kinase expression library, we identified mitogen-activated protein kinase kinase kinase 8 (MAP3K8/Tpl2) as a positive regulator of murine gammaherpesvirus 68 (MHV-68 or gammaHV-68) lytic gene expression and replication. Tpl2 enhances MHV-68 lytic replication by upregulating lytic gene expression and promoter activities of viral lytic genes, including RTA and open reading frame 57 (ORF57). By screening a cellular transcription factor library, we identified the Fos AP-1 transcription factor as a downstream factor that is both necessary and sufficient for mediating the enhancement of MHV-68 lytic replication by Tpl2. In addition, Tpl2 stimulates the promoter activities of key viral lytic genes, including RTA and ORF57, in an AP-1-dependent manner. We identified an AP-1-responsive element on the MHV-68 RTA promoter as the cis element mediating the upregulation of RTA promoter activity by Tpl2. MHV-68 lytic infection upregulates Fos expression, AP-1 activity, and RTA promoter activity in a Tpl2-dependent manner. We constructed a mutant MHV-68 virus that abolished this AP-1-responsive element. This mutant virus exhibited attenuated lytic replication kinetics, indicative of a critical role of this AP-1-responsive element during lytic replication. Moreover, Tpl2 knockdown inhibited the lytic replication of wild-type MHV-68 (MHV-68-WT) but not that of the MHV-68 mutant virus, indicating that endogenous Tpl2 promotes efficient virus lytic replication through AP-1-dependent upregulation of RTA expression. In summary, through tandem functional screens, we identified the Tpl2/AP-1 signaling transduction pathway as a positive regulator of MHV-68 lytic replication.
Li
Xudong
X
Department of Molecular and Medical Pharmacology, UCLA David Geffen School of Medicine, Los Angeles, California 90095, USA.
Feng
Jun
J
Chen
Shijia
S
Peng
Li
L
He
Wei-Wu
WW
Qi
Jing
J
Deng
Hongyu
H
Sun
Ren
R
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004279:DNA, Viral / Q000235:genetics; D005814:Genes, Viral; D054884:Host-Pathogen Interactions / Q000235:genetics / Q000502:physiology; D006801:Humans; D017874:Immediate-Early Proteins / Q000235:genetics / Q000502:physiology; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D051379:Mice; D008954:Models, Biological; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D018144:Rhadinovirus / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000502:physiology*; D014709:Vero Cells; D014779:Virus Replication / Q000235:genetics / Q000502:physiology*
D004279:DNA, Viral; D017874:Immediate-Early Proteins; D011518:Proto-Oncogene Proteins; D011994:Recombinant Proteins; D015534:Trans-Activators; D018808:Transcription Factor AP-1; D020930:MAP Kinase Kinase Kinases; C069937:MAP3K8 protein, human