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Updated: May 5, 2026

Application of Laser Micro-irradiation for Examination of Single and Double Strand Break Repair in Mammalian Cells
Published on: September 5, 2017
XRCC1 stimulates human polynucleotide kinase activity at damaged DNA termini and accelerates DNA single-strand break
C J Whitehouse1, R M Taylor, A Thistlethwaite
1School of Biological Sciences, G.38 Stopford Building, University of Manchester, Oxford Road M13 9PT, United Kingdom.
Abstract:
XRCC1 protein is required for DNA single-strand break repair and genetic stability but its biochemical role is unknown. Here, we report that XRCC1 interacts with human polynucleotide kinase in addition to its established interactions with DNA polymerase-beta and DNA ligase III. Moreover, these four proteins are coassociated in multiprotein complexes in human cell extract and together they repair single-strand breaks typical of those induced by reactive oxygen species and ionizing radiation. Strikingly, XRCC1 stimulates the DNA kinase and DNA phosphatase activities of polynucleotide kinase at damaged DNA termini and thereby accelerates the overall repair reaction. These data identify a novel pathway for mammalian single-strand break repair and demonstrate a concerted role for XRCC1 and PNK in the initial step of processing damaged DNA ends.
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Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
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