title: Transcriptional activation of Epstein-Barr virus BRLF1 by USF1 and Rta.
abstract: During its lytic cycle, Epstein-Barr virus (EBV) expresses Rta, a factor encoded by BRLF1 that activates the transcription of viral lytic genes. We found that upstream stimulating factor (USF) binds to E1, one of the five E boxes located at - 79 in the BRLF1 promoter (Rp), to activate BRLF1 transcription. Furthermore, Rta was shown to interact with USF1 in coimmunoprecipitation and glutathione S-transferase (GST)-pulldown assays, and confocal laser-scanning microscopy further confirmed that these two proteins colocalize in the nucleus. Rta was also found to bind with the E1 sequence in a biotin-labelled E1 probe, but only in the presence of USF1, suggesting that these two proteins likely form a complex on E1. We subsequently constructed p188mSZ, a reporter plasmid that contained the sequence from - 188 to +5 in Rp, within which the Sp1 site and Zta response element were mutated. In EBV-negative Akata cells cotransfected with p188mSZ and plasmids expressing USF1 and Rta, synergistic activation of Rp transcription was observed. However, after mutating the E1 sequence in p188mSZ, USF1 and Rta were no longer able to transactivate Rp, indicating that Rta autoregulates BRLF1 transcription via its interaction with USF1 on E1. This study showed that pUSF1 transfection after EBV lytic induction in P3HR1 cells increases Rta expression, indicating that USF1 activates Rta expression after the virus enters the lytic cycle. Together, these results reveal a novel mechanism by which USF interacts with Rta to promote viral lytic development, and provide additional insight into the viral-host interactions of EBV.
authors: Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.
authors: Chen-Chia
authors: CC
authors: Hung
authors: Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.
authors: Chung-Wen
authors: CW
authors: Kuo
authors: Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.
authors: Wen-Hung
authors: WH
authors: Wang
authors: Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.
authors: Tzu-Hsuan
authors: TH
authors: Chang
authors: Graduate Institute of Clinical Medical Sciences, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.
authors: Pey-Jium
authors: PJ
authors: Chang
authors: Department of Biochemical Science and Technology, College of Life Science, National Taiwan University, Taipei 10617, Taiwan, ROC.
authors: Li-Kwan
authors: LK
authors: Chang
authors: Molecular Genetics Laboratory, Department of Microbiology and Immunology, Chang-Gung University, Kwei-Shan, Taoyuan 33302, Taiwan, ROC.|Department of Medical Research, Chang-Gung Memorial Hospital Chiayi Branch, Chiayi 61363, Taiwan, ROC.
authors: Shih-Tung
authors: ST
authors: Liu
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D020031:Epstein-Barr Virus Infections / Q000235:genetics / Q000378:metabolism* / Q000821:virology; D015967:Gene Expression Regulation, Viral; D004854:Herpesvirus 4, Human / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D054884:Host-Pathogen Interactions; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015533:Transcriptional Activation; D051720:Upstream Stimulatory Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: C068382:BRLF1 protein, Human herpesvirus 4; C063676:BZLF1 protein, Herpesvirus 4, Human; D017874:Immediate-Early Proteins; D015534:Trans-Activators; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors