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A novel splice variant of the DNA-PKcs gene is associated with clinical and cellular radiosensitvity in a xeroderma pigmentosum patient.
  1. Fatemeh Abbaszadeh (fatemeh.abbaszadeh{at}icr.ac.uk)
  1. Institute of Cancer Researh, Royal Marsden Hospital, Surrey, United Kingdom
    1. Peter H Clingen (p.clingen{at}hotmail.com)
    1. University College London Cancer Institute, United Kingdom
      1. Colin F Arlett (colin-a{at}solutions-inc.co.uk)
      1. University of Sussex, United Kingdom
        1. Piers N Plowman (nick.plowman{at}bartsandthelondon.nhs.uk)
        1. Bart's and the London Hospital, United Kingdom
          1. Emma C Bourton (emma.bourton{at}brunel.ac.uk)
          1. Brunel University, United Kingdom
            1. Matthew Themis (matthew.themis{at}brunel.ac.uk)
            1. Brunel University, United Kingdom
              1. Evgeny M Makarov (evgeny.makarov{at}brunel.ac.uk)
              1. Brunel University, United Kingdom
                1. Robert F Newbold (robert.newbold{at}brunel.ac.uk)
                1. Brunel University, United Kingdom
                  1. Michael H Green (m.h.l.green{at}brighton.ac.uk)
                  1. Brighton University, United Kingdom
                    1. Christopher N Parris (christopher.parris{at}brunel.ac.uk)
                    1. Brunel University, United Kingdom

                      Abstract

                      Background: Radiotherapy-induced DNA double strand breaks (DSB) are critical cytotoxic lesions. Inherited defects in DSB DNA repair pathways lead to hypersensitivity to ionising radiation, immunodeficiency and increased cancer incidence. A patient with xeroderma pigmentosum complementation group C, with a scalp angiosarcoma exhibited dramatic clinical radiosensitivity following radiotherapy, resulting in death. A fibroblast cell line from non-affected skin (XP14BRneo17) was hypersensitive to ionising radiation and defective in DNA double strand break repair.

                      Aim: To determine the genetic defect causing cellular radiation hypersensitivity in XP14BRneo17 cells.

                      Methods: Functional genetic complementation whereby copies of human chromosomes containing genes involved in DNA DSB repair (chromosomes 2, 5, 8 10, 13 and 22) were individually transferred to XP14BRneo17 cells in an attempt to correct the radiation hypersensitivity. Clonogenic survival assays and γ-H2AX immunofluorescence were conducted to measure radiation sensitivity and repair of DNA DSBs. DNA sequencing of defective DNA repair genes was performed.

                      Results: Transfer of chromosome 8 (location of DNA-PKcs gene), and transfection of a mammalian expression construct containing the DNA-PKcs cDNA restored normal ionising radiation sensitivity and repair of DNA DSBs in XP14BRneo17 cells. DNA sequencing of the DNA-PKcs coding region revealed a 249 bp deletion (between base pairs 3656-3904) encompassing exon 31 of the gene.

                      Conclusion: We provide evidence of a novel splice variant of the DNA-PKcs gene associated with radiosensitivity in a xeroderma pigmentosum patient and report the first double mutant in distinct DNA repair pathways being consistent with viability.

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