Pathological mutations in PNKP trigger defects in DNA single-strand break repair but not DNA double-strand break repair.

Abstract

Hereditary mutations in polynucleotide kinase-phosphatase (PNKP) result in a spectrum of neurological pathologies ranging from neurodevelopmental dysfunction in microcephaly with early onset seizures (MCSZ) to neurodegeneration in ataxia oculomotor apraxia-4 (AOA4) and Charcot-Marie-Tooth disease (CMT2B2). Consistent with this, PNKP is implicated in the repair of both DNA single-strand breaks (SSBs) and DNA double-strand breaks (DSBs); lesions that can trigger neurodegeneration and neurodevelopmental dysfunction, respectively. Surprisingly, however, we did not detect a significant defect in DSB repair (DSBR) in primary fibroblasts from PNKP patients spanning the spectrum of PNKP-mutated pathologies. In contrast, the rate of SSB repair (SSBR) is markedly reduced. Moreover, we show that the restoration of SSBR in patient fibroblasts collectively requires both the DNA kinase and DNA phosphatase activities of PNKP, and the fork-head associated (FHA) domain that interacts with the SSBR protein, XRCC1. Notably, however, the two enzymatic activities of PNKP appear to affect different aspects of disease pathology, with reduced DNA phosphatase activity correlating with neurodevelopmental dysfunction and reduced DNA kinase activity correlating with neurodegeneration. In summary, these data implicate reduced rates of SSBR, not DSBR, as the source of both neurodevelopmental and neurodegenerative pathology in PNKP-mutated disease, and the extent and nature of this reduction as the primary determinant of disease severity.

• Authors: Ilona Kalasova, Richard Hailstone, Janin Bublitz, Jovel Bogantes, Winfried Hofmann, Alejandro Leal, Hana Hanzlikova, Keith W Caldecott
• Journal: Nucleic acids research (Nucleic Acids Res) Vol. 48 Issue 12 Pg. 6672-6684 (07 09 2020) ISSN: 1362-4962 [Electronic] England
• PMID: 32504494 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © The Author(s) 2020. Published by Oxford University Press on behalf of Nucleic Acids Research.

Chemical References

• X-ray Repair Cross Complementing Protein 1
• XRCC1 protein, human
• PNKP protein, human
• Phosphotransferases (Alcohol Group Acceptor)
• DNA Repair Enzymes

Topics

• Apraxias (genetics, pathology)
• Charcot-Marie-Tooth Disease (genetics, pathology)
• DNA Breaks, Double-Stranded
• DNA Breaks, Single-Stranded
• DNA Repair (genetics)
• DNA Repair Enzymes (genetics)
• Fibroblasts (metabolism, pathology)
• Humans
• Microcephaly (genetics, pathology)
• Mutation (genetics)
• Phosphotransferases (Alcohol Group Acceptor) (genetics)
• Seizures (genetics, pathology)
• X-ray Repair Cross Complementing Protein 1 (genetics)