title: Kaposi's sarcoma-associated herpesvirus induces the ATM and H2AX DNA damage response early during de novo infection of primary endothelial cells, which play roles in latency establishment.
abstract: The DNA damage response (DDR) that evolved to repair host cell DNA damage also recognizes viral DNA entering the nucleus during infections. Here, we investigated the modulation of DDR signaling during de novo infection of primary endothelial cells by Kaposi's sarcoma-associated herpesvirus (KSHV). Phosphorylation of representative DDR-associated proteins, such as ataxia telangiectasia mutated (ATM) and H2AX, was induced as early as 30 min (0.5 h) postinfection and persisted during in vitro KSHV latency. Phosphorylated H2AX (γH2AX) colocalized at 30 min (0.5 h) with the KSHV genome entering the nuclei. Total H2AX protein levels also increased, and the increase was attributed to a decrease in degradative H2AX Lys48-linked polyubiquitination with a concomitant increase in Lys63-linked polyubiquitination that was shown to increase protein stability. ATM and H2AX phosphorylation and γH2AX nuclear foci were also induced by UV-inactivated KSHV, which ceased at later times of infection. Inhibition of ATM kinase activity by KU-55933 and H2AX knockdown by small interfering RNA significantly reduced the expression of the KSHV latency-associated nuclear antigen 1 (LANA-1; ORF73) and LANA-1 nuclear puncta. Knockdown of H2AX also resulted in a >80% reduction in the nuclear KSHV DNA copy numbers. Similar results were also observed in ATM-negative cells, although comparable levels of viral DNA entered ATM-negative and ATM-positive cell nuclei. In contrast, knockdown of CHK1 and CHK2 did not affect ORF73 expression. Collectively, these results demonstrate that KSHV induces ATM and H2AX, a selective arm of the DDR, for the establishment and maintenance of its latency during de novo infection of primary endothelial cells.
  
  
  OBJECTIVE
  Eukaryotic cells mount a DNA damage response (DDR) to sense and repair different types of cellular DNA damage. In addition, DDR also recognizes exogenous genetic material, such as the viral DNA genome entering the nucleus during infections. The present study was undertaken to determine whether de novo Kaposi's sarcoma-associated herpesvirus (KSHV) infection modulates DDR. Our results demonstrate that early during de novo infection of primary endothelial cells, KSHV induces a selective arm of DDR signaling, such as the ATM kinase and its downstream target, H2AX, which are essential for KSHV's latent gene expression and the establishment of latency. These studies suggest that targeting ATM and H2AX could serve as an attractive strategy to block the establishment of KSHV latent infection and the associated malignancies.
authors.affiliation: H. M. Bligh Cancer Research Laboratories, Department of Microbiology and Immunology, Chicago Medical School, Rosalind Franklin University of Medicine and Science, North Chicago, Illinois, USA.
authors.forename: Vivek Vikram
authors.initials: VV
authors.lastname: Singh
authors.forename: Dipanjan
authors.initials: D
authors.lastname: Dutta
authors.forename: Mairaj Ahmed
authors.initials: MA
authors.lastname: Ansari
authors.forename: Sujoy
authors.initials: S
authors.lastname: Dutta
authors.forename: Bala
authors.initials: B
authors.lastname: Chandran
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics; D000956:Antigens, Viral / Q000235:genetics / Q000378:metabolism; D064007:Ataxia Telangiectasia Mutated Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000071877:Checkpoint Kinase 1; D064447:Checkpoint Kinase 2 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D042783:Endothelial Cells / Q000821:virology*; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D055785:Gene Knockdown Techniques; D016679:Genome, Viral; D006566:Herpesviridae Infections / Q000235:genetics / Q000378:metabolism; D019288:Herpesvirus 8, Human / Q000502:physiology*; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008954:Models, Biological; D009025:Morpholines / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D011753:Pyrones / Q000494:pharmacology; D015398:Signal Transduction; D014764:Viral Proteins / Q000235:genetics; D017735:Virus Latency / Q000235:genetics
chemical_list: C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; D034961:Antigens, Nuclear; D000956:Antigens, Viral; C468783:H2AX protein, human; D006657:Histones; D009025:Morpholines; D009687:Nuclear Proteins; D011753:Pyrones; D014764:Viral Proteins; C109540:latency-associated nuclear antigen; C583446:latent Orf73 antigen, human herpesvirus 8; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1