title: Interaction between HIV-1 Tat and DNA-PKcs modulates HIV transcription and class switch recombination.
abstract: HIV-1 tat targets a variety of host cell proteins to facilitate viral transcription and disrupts host cellular immunity by inducing lymphocyte apoptosis, but whether it influences humoral immunity remains unclear. Previously, our group demonstrated that tat depresses expression of DNA-PKcs, a critical component of the non-homologous end joining pathway (NHEJ) of DNA double-strand breaks repair, immunoglobulin class switch recombination (CSR) and V(D)J recombination, and sensitizes cells to ionizing radiation. In this study, we demonstrated that HIV-1 Tat down-regulates DNA-PKcs expression by directly binding to the core promoter sequence. In addition, Tat interacts with and activates the kinase activity of DNA-PKcs in a dose-dependent and DNA independent manner. Furthermore, Tat inhibits class switch recombination (CSR) at low concentrations (≤ 4 µg/ml) and stimulates CSR at high concentrations (≥ 8 µg/ml). On the other hand, low protein level and high kinase activity of DNA-PKcs promotes HIV-1 transcription, while high protein level and low kinase activity inhibit HIV-1 transcription. Co-immunoprecipitation results revealed that DNA-PKcs forms a large complex comprised of Cyclin T1, CDK9 and Tat via direct interacting with CDK9 and Tat but not Cyclin T1. Taken together, our results provide new clues that Tat regulates host humoral immunity via both transcriptional depression and kinase activation of DNA-PKcs. We also raise the possibility that inhibitors and interventions directed towards DNA-PKcs may inhibit HIV-1 transcription in AIDS patients.
authors.affiliation: 1. Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine, 100850, Beijing, China;
authors.forename: Shi-Meng
authors.initials: SM
authors.lastname: Zhang
authors.affiliation: 1. Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine, 100850, Beijing, China;
authors.forename: He
authors.initials: H
authors.lastname: Zhang
authors.affiliation: 1. Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine, 100850, Beijing, China;
authors.forename: Tian-Yi
authors.initials: TY
authors.lastname: Yang
authors.affiliation: 2. The State Key Laboratory of NBC Protection for Civilian, 102205, Beijing, China;
authors.forename: Tian-Yi
authors.initials: TY
authors.lastname: Ying
authors.affiliation: 3. Beijing Institute of Health Administration and Medical Information, 100850, Beijing, China;
authors.forename: Pei-Xiang
authors.initials: PX
authors.lastname: Yang
authors.affiliation: 1. Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine, 100850, Beijing, China;
authors.forename: Xiao-Dan
authors.initials: XD
authors.lastname: Liu
authors.affiliation: 4. Shandong Provincial Key Laboratory of Plastic and Microscopic Repair Technology, Institute of Plastic Surgery, Weifang Medical University, 261053, Weifang, Shandong Province, China.
authors.forename: Sheng-Jian
authors.initials: SJ
authors.lastname: Tang
authors.affiliation: 1. Department of Radiation Toxicology and Oncology; Beijing Institute of Radiation Medicine, 100850, Beijing, China;
authors.forename: Ping-Kun
authors.initials: PK
authors.lastname: Zhou
mesh_terms: D017931:DNA Primers / Q000235:genetics; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005434:Flow Cytometry; D015967:Gene Expression Regulation, Viral / Q000235:genetics / Q000502:physiology*; D057809:HEK293 Cells; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D056724:Immunity, Humoral / Q000276:immunology*; D017578:Immunoglobulin Class Switching / Q000502:physiology*; D047468:Immunoprecipitation; D008156:Luciferases; D013601:T-Lymphocytes; D014158:Transcription, Genetic / Q000235:genetics*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000276:immunology / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D054322:tat Gene Products, Human Immunodeficiency Virus; D008156:Luciferases; D051747:DNA-Activated Protein Kinase
keywords: DNA-PKcs; HIV-1 tat