title: Chromatin remodeling of the Kaposi's sarcoma-associated herpesvirus ORF50 promoter correlates with reactivation from latency.
abstract: The switch from latent to lytic infection of Kaposi's sarcoma-associated herpesvirus is initiated by the immediate early transcriptional activator protein Rta/open reading frame 50 (ORF50). We examined the transcriptional regulation of the ORF50 core promoter in response to lytic cycle stimulation. We show that the ORF50 promoter is highly responsive to sodium butyrate (NaB) and trichostatin A (TSA), two chemicals known to inhibit histone deacetylases. The NaB and TSA responsive element was mapped to a 70-bp minimal promoter containing an essential GC box that binds Sp1/Sp3 in vitro and in vivo. Micrococcal nuclease mapping studies revealed that a nucleosome is positioned over the transcriptional initiation and the Sp1/3 binding sites. Stimulation with NaB or TSA increased histone acetylation and restriction enzyme accessibility of the ORF50 promoter transcription initiation site. Chromatin immunoprecipitation assay was used to demonstrate that the ORF50 promoter is associated with several different histone deacetylase proteins (including HDAC1, 5, and 7) in latently infected cells. NaB treatment led to the rapid association of Ini1/Snf5, a component of the Swi/Snf family of chromatin remodeling proteins, with the ORF50 promoter. Ectopic expression of the CREB-binding protein (CBP) histone acetyltransferase (HAT) stimulated plasmid-based ORF50 transcription in a HAT-dependent manner, suggesting that CBP recruitment to the ORF50 promoter can be an initiating event for transcription and viral reactivation. Together, these results suggest that remodeling of a stably positioned nucleosome at the transcriptional initiation site of ORF50 is a regulatory step in the transition from latent to lytic infection.
authors.affiliation: The Wistar Institute. Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Lu
authors.forename: Jing
authors.initials: J
authors.lastname: Zhou
authors.forename: Andreas
authors.initials: A
authors.lastname: Wiedmer
authors.forename: Kevin
authors.initials: K
authors.lastname: Madden
authors.forename: Yan
authors.initials: Y
authors.lastname: Yuan
authors.forename: Paul M
authors.initials: PM
authors.lastname: Lieberman
mesh_terms: D001483:Base Sequence; D002087:Butyrates / Q000494:pharmacology; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000502:physiology*; D002868:Chromosomal Proteins, Non-Histone; D015967:Gene Expression Regulation, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009707:Nucleosomes; D011401:Promoter Regions, Genetic; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014775:Virus Activation; D017735:Virus Latency
chemical_list: D002087:Butyrates; D002843:Chromatin; D002868:Chromosomal Proteins, Non-Histone; D006877:Hydroxamic Acids; D017874:Immediate-Early Proteins; D009707:Nucleosomes; C417604:Rta protein, Human herpesvirus 8; C445179:SWI-SNF-B chromatin-remodeling complex; D015534:Trans-Activators; D014157:Transcription Factors; D014764:Viral Proteins; C012589:trichostatin A