title: The lytic switch protein of KSHV activates gene expression via functional interaction with RBP-Jkappa (CSL), the target of the Notch signaling pathway.
abstract: The RTA protein of the Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is responsible for the switch from latency to lytic replication, a reaction essential for viral spread and KS pathogenesis. RTA is a sequence-specific transcriptional activator, but the diversity of its target sites suggests it may act via interaction with host DNA-binding proteins as well. Here we show that KSHV RTA interacts with the RBP-Jkappa protein, the primary target of the Notch signaling pathway. This interaction targets RTA to RBP-Jkappa recognition sites on DNA and results in the replacement of RBP-Jkappa's intrinsic repressive action with activation mediated by the C-terminal domain of RTA. Mutation of such sites in target promoters strongly impairs RTA responsiveness. Similarly, such target genes are induced poorly or not at all by RTA in fibroblasts derived from RBP-Jkappa(-/-) mice, a defect that can be reversed by expression of RBP-Jkappa. In vitro, RTA binds to two adjacent regions of RBP-Jkappa, one of which is identical to the central repression domain that binds the Notch effector fragment. These results indicate that KSHV has evolved a ligand-independent mechanism for constitutive activation of the Notch pathway as a part of its strategy for reactivation from latency.
authors.affiliation: Howard Hughes Medical Institute and Departments of Microbiology and Medicine, University of California, San Francisco, California 94143-0414, USA.
authors.forename: Yuying
authors.initials: Y
authors.lastname: Liang
authors.forename: Jean
authors.initials: J
authors.lastname: Chang
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lynch
authors.forename: David M
authors.initials: DM
authors.lastname: Lukac
authors.forename: Don
authors.initials: D
authors.lastname: Ganem
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000502:physiology; D005347:Fibroblasts / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D019288:Herpesvirus 8, Human / Q000235:genetics / Q000502:physiology*; D017874:Immediate-Early Proteins / Q000502:physiology*; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D008565:Membrane Proteins / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D051880:Receptors, Notch; D011993:Recombinant Fusion Proteins / Q000502:physiology; D012097:Repressor Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*; D020798:Two-Hybrid System Techniques; D014764:Viral Proteins / Q000502:physiology*; D017735:Virus Latency; D014779:Virus Replication
chemical_list: D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D051819:Immunoglobulin J Recombination Signal Sequence-Binding Protein; D008565:Membrane Proteins; D009687:Nuclear Proteins; C497571:Rbpj protein, mouse; D051880:Receptors, Notch; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C417604:Rta protein, Human herpesvirus 8; D015534:Trans-Activators; D014764:Viral Proteins; D004247:DNA