Deacetylase inhibitors and the viral transactivator TaxBLV synergistically activate bovine leukemia virus gene expression via a cAMP-responsive element- and cAMP-responsive element-binding protein-dependent mechanism.
Efficient bovine leukemia virus (BLV) transcription requires the virus-encoded transactivator Tax(BLV), which acts through three Tax(BLV)-responsive elements located in the 5' long terminal repeat. It has been proposed that the binding of the CRE-binding protein (CREB) and the activating transcription factor (ATF) to the three imperfect cAMP-responsive elements (CREs) located in each Tax(BLV)-responsive element mediates Tax(BLV) transactivation. Here we demonstrated that deacetylase inhibitors (HDACis) synergistically enhanced the transcriptional activation of the BLV promoter by Tax(BLV) in a CRE-dependent manner. Tax(BLV) was acetylated in vivo at its N(alpha) terminus but not at internal lysine residues. Rather, HDACi potentiation of Tax(BLV) transactivation was mediated by an HDACi indirect action that requires new protein synthesis. Mechanistically, using a dominant-negative form of CREB, we showed that Tax(BLV) and HDACi synergistically activated BLV gene expression via a CREB-dependent mechanism. Moreover, electrophoretic mobility shift assay and Western blot experiments revealed that HDACi increased the in vitro DNA binding activity of CREB/ATF but did not alter CREB/ATF intranuclear presence. Remarkably, chromatin immunoprecipitation assays demonstrated that HDACi treatment increased the level of CREB bound to the BLV promoter in vivo. Our results together suggest that an increase in CREB/ATF occupancy of the viral CREs in response to HDACi potentiates Tax(BLV) transactivation of the BLV promoter.
Nguyên
Thi Liên-Anh
TL
Université Libre de Bruxelles, Institut de Biologie et de Médecine Moléculaires, Service de Chimie Biologique, Laboratoire de Virologie Moléculaire, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium.
Calomme
Claire
C
Wijmeersch
Gaëlle
G
Nizet
Séverine
S
Veithen
Emmanuelle
E
Portetelle
Daniel
D
de Launoit
Yvan
Y
Burny
Arsène
A
Van Lint
Carine
C
D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002352:Carrier Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D002875:Chromosomes / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D016356:Gene Products, tax / Q000235:genetics*; D005799:Genes, Dominant; D005822:Genetic Vectors; D006801:Humans; D006867:Hydrolases / Q000037:antagonists & inhibitors*; D001909:Leukemia Virus, Bovine / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D020218:Response Elements; D012260:Ribonucleases / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D002352:Carrier Proteins; D002843:Chromatin; D002373:Cyclic AMP Receptor Protein; D017362:Cyclic AMP Response Element-Binding Protein; D016356:Gene Products, tax; D012333:RNA, Messenger; D000242:Cyclic AMP; D008156:Luciferases; D006867:Hydrolases; D012260:Ribonucleases