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Sensing Foreign DNA: The Role of DNA-PKcs in Human Anti-viral Innate Immunity



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Hristova, Dayana 


Host cell pattern recognition receptors (PRRs) are a first line of defence against pathogens and function to generate a productive innate immune response. PRRs sense pathogen-associated molecular patterns (PAMPs), such as viral genomic DNA, which is a major PAMP during DNA virus infection. Viral DNA sensing leads to the activation of the STING-TBK1-IRF3 signalling axis and the production of type I interferon. Previously, our work identified the non-homologous end-joining protein DNA-PKcs, part of the DNA-dependent protein kinase (DNA-PK) complex, as an intracellular PRR for cytoplasmic viral DNA in murine cells. After screening several human cell lines, we established a robust system to dissect the DNA sensing pathway in human fibroblasts. In these human cells DNA-PKcs was found to be essential for the production of type I interferon via the STING pathway in response to DNA and DNA virus infection and we found that the kinase activity of DNA-PKcs was not required for this response. Many DNA viruses evade the immune response by inhibiting the pathway. We make use of attenuated Herpes simplex virus 1 (HSV- 1) and Vaccinia virus (VACV) that lack immunomodulatory proteins and drive type I interferon production. DNA-PKcs-/- cells have a defective immune response after infection with attenuated HSV and VACV. Furthermore, primary patient fibroblasts harbouring a mutation in DNA-PKcs showed a gain-of-function effect and an enhanced immune signaling to DNA and DNA virus infection. DNA-PKcs has also been linked to cell death during retrovirus integration although this has not been studied extensively. We carried out some preliminary work in this study, showing that DNA-PKcs-/- cells are more prone to cell death during HSV-1 infection and have reduced yields of virion production. This work demonstrates the role of DNA-PKcs as a viral DNA sensor in human cells and adds to the knowledge of the DNA sensing processes that are essential for anti-viral innate immunity.





Ferguson, Brian


innate immunity, nucleic acid sensing, pattern recognition receptors, viral infection


Doctor of Philosophy (PhD)

Awarding Institution

University of Cambridge
Wellcome Trust (201946/Z/16/Z)
Biotechnology and Biological Sciences Research Council (BB/S001336/1)
Cambridge Philosophical Society