The viral protein A238L inhibits TNF-alpha expression through a CBP/p300 transcriptional coactivators pathway.
African swine fever virus (ASFV) is able to inhibit TNF-alpha-induced gene expression through the synthesis of A238L protein. This was shown by the use of deletion mutants lacking the A238L gene from the Vero cell-adapted Ba71V ASFV strain and from the virulent isolate E70. To further analyze the molecular mechanism by which the viral gene controls TNF-alpha, we have used Jurkat cells stably transfected with the viral gene to identify the TNF-alpha regulatory elements involved in the induction of the gene after stimulation with PMA and calcium ionophore. We have thus identified the cAMP-responsive element and kappa3 sites on the TNF-alpha promoter as the responsible of the gene activation, and demonstrate that A238L inhibits TNF-alpha expression through these DNA binding sites. This inhibition was partially reverted by overexpression of the transcriptional factors NF-AT, NF-kappaB, and c-Jun. Furthermore, we present evidence that A238L inhibits the activation of TNF-alpha by modulating NF-kappaB, NF-AT, and c-Jun trans activation through a mechanism that involves CREB binding protein/p300 function, because overexpression of these transcriptional coactivators recovers TNF-alpha promoter activity. In addition, we show that A238L is a nuclear protein that binds to the cyclic AMP-responsive element/kappa3 complex, thus displacing the CREB binding protein/p300 coactivators. Taken together, these results establish a novel mechanism in the control of TNF-alpha gene expression by a viral protein that could represent an efficient strategy used by ASFV to evade the innate immune response.
Granja
Aitor G
AG
Centro de Biología Molecular "Severo Ochoa" (Consejo Superior de Investigaciones Cientificas-Universidad Autónoma de Madrid), Universidad Autónoma de Madrid, Madrid, Spain.
Nogal
Maria L
ML
Hurtado
Carolina
C
Del Aguila
Carmen
C
Carrascosa
Angel L
AL
Salas
María L
ML
Fresno
Manuel
M
Revilla
Yolanda
Y
D051696:Activating Transcription Factors / Q000235:genetics / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002522:Chlorocebus aethiops; D051786:Cyclic AMP Response Element Modulator / Q000235:genetics; D005455:Fluorescent Antibody Technique; D015967:Gene Expression Regulation, Viral; D006801:Humans; D019169:Jurkat Cells; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism; D011401:Promoter Regions, Genetic; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis / Q000235:genetics*; D014709:Vero Cells; D014764:Viral Proteins / Q000378:metabolism*
C113585:A238L protein, African swine fever virus; D051696:Activating Transcription Factors; C451405:CITED4 protein, human; D016328:NF-kappa B; D050778:NFATC Transcription Factors; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D014764:Viral Proteins; D051786:Cyclic AMP Response Element Modulator