Review
Tidying up loose ends: the role of polynucleotide kinase/phosphatase in DNA strand break repair

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The termini of DNA strand breaks induced by internal and external factors often require processing before missing nucleotides can be replaced by DNA polymerases and the strands rejoined by DNA ligases. Polynucleotide kinase/phosphatase (PNKP) serves a crucial role in the repair of DNA strand breaks by catalyzing the restoration of 5′-phosphate and 3′-hydroxyl termini. It participates in several DNA repair pathways through interactions with other DNA repair proteins, notably XRCC1 and XRCC4. Recent studies have highlighted the physiological importance of PNKP in maintaining the genomic stability of normal tissues, particularly developing neural cells, as well as enhancing the resistance of cancer cells to genotoxic therapeutic agents.

Section snippets

Polynucleotide kinase/phosphatase: an essential enzyme for the repair of damaged DNA termini

Damage to cellular DNA is considered to be a significant factor in aging [1], cancer etiology and treatment 2, 3, 4, and neurological disorders [5]. DNA damage, in the form of base modification, base loss and strand breaks, can be triggered by intracellular agents, primarily reactive oxygen species (ROS), as well as by exogenous agents. As a result, cells have evolved a battery of repair pathways to counter the mutational and cytotoxic consequences of DNA damage [6]. Strand breaks can be

Molecular architecture of PNKP

PNKP is a multidomain enzyme that consists of an N-terminal forkhead-associated (FHA) domain and a C-terminal catalytic domain composed of fused phosphatase and kinase subdomains. The FHA domain is linked to the catalytic domain through a flexible polypeptide segment and acts to selectively bind acidic casein kinase 2 (CK2)-phosphorylated regions in XRCC1 [14] and XRCC4 [15], which are key scaffolding proteins in the repair of DNA SSBs and DSBs, respectively. The DNA repair factors aprataxin

PNKP and single-strand break repair (SSBR)

SSBR is a multienzyme pathway that employs different players depending on the causative agent. In the case of IR-induced strand breaks, which typically involve the loss of at least one nucleotide, the initial process of damage recognition and correction of the strand break termini is primarily carried out by poly(ADP-ribose) polymerase (PARP), XRCC1, AP endonuclease I (APE1) and/or PNKP, although other proteins, such as tyrosyl-DNA phosphodiesterase (TDP1) and aprataxin might provide backup

PNKP and base excision repair (BER)

BER is responsible for the repair of most minor base modifications induced by IR, ROS and alkylating agents. The first step is removal of the modified base by DNA glycosylase followed by cleavage of the DNA at the newly formed apurinic/apyrimidinic (AP) site by APE1 [44]. Alternatively, the glycosylase might have AP lyase activity that hydrolyzes the AP site [44]. The involvement of PNKP in the BER pathway became evident after the discovery of the nei endonuclease VIII-like-1 (NEIL1) and NEIL2

PNKP and double-strand break repair (DSBR)

Of the two major DSBR pathways, there is clear evidence for PNKP participation in nonhomologous end joining (NHEJ) 15, 47, 48, but the failure to influence IR-induced sister chromatid exchange by PNKP depletion suggests that PNKP is not involved in homologous recombination [48]. PNKP also plays a role in a back-up, XRCC1-dependent, DSB repair pathway [49]. Evidence for PNKP participation in NHEJ came initially from experiments using human cell-free extracts, showing that the PNKP kinase

Physiological roles and clinical potential of PNKP

The increased interest in PNKP reflects its involvement in several DNA repair pathways that protect cells from endogenous and exogenous genotoxic agents. Disruption of NHEJ genes and SSBR/BER genes are known to cause neurological disorders with various symptoms; for example, microcephaly is seen in individuals with mutations in LIG4 (which encodes DNA ligase IV) [53], whereas deletion of Xrcc1 in mice causes seizures [54]. A recent report established that a severe neurological autosomal

Concluding remarks

PNKP is a key enzyme in the cellular processing of stand break termini and not surprisingly participates in several DNA repair pathways (summarized in Figure 3). Further progress is required to clarify its regulation, interactions with other repair enzymes and physiological role in neurons and other tissues. Because of its involvement in a variety of repair pathways, PNKP is now regarded as a therapeutic target in the treatment of cancer and thus new inhibitory compounds will need to be

Acknowledgments

We thank Dr Susan Lees-Miller (University of Calgary) for critically reading the manuscript. This work was supported by grants from the Canadian Institutes of Health Research, the Canadian Cancer Society, the Alberta Cancer Foundation, and the National Institutes of Health. J.N.M.G. acknowledges the support of the Howard Hughes International Scholar program.

References (74)

  • E.V. Koonin et al.

    Computer analysis of bacterial haloacid dehalogenases defines a large superfamily of hydrolases with diverse specificity. Application of an iterative approach to database search

    J. Mol. Biol.

    (1994)
  • D. Durocher et al.

    The FHA domain

    FEBS Lett.

    (2002)
  • L. Wiederhold

    AP endonuclease-independent DNA base excision repair in human cells

    Mol. Cell

    (2004)
  • C.J. Whitehouse

    XRCC1 stimulates human polynucleotide kinase activity at damaged DNA termini and accelerates DNA single-strand break repair

    Cell

    (2001)
  • R.S. Mani

    XRCC1 stimulates polynucleotide kinase by enhancing its damage discrimination and displacement from DNA repair intermediates

    J. Biol. Chem.

    (2007)
  • J.L. Parsons

    XRCC1 phosphorylation by CK2 is required for its stability and efficient DNA repair

    DNA Repair (Amst.)

    (2010)
  • M. Meijer

    Pnk1, a DNA kinase/phosphatase required for normal response to DNA damage by gamma-radiation or camptothecin in Schizosaccharomyces pombe

    J. Biol. Chem.

    (2002)
  • I. Plo

    Association of XRCC1 and tyrosyl DNA phosphodiesterase (Tdp1) for the repair of topoisomerase I-mediated DNA lesions

    DNA Repair (Amst.)

    (2003)
  • T. Zhou

    Tyrosyl-DNA phosphodiesterase and the repair of 3′-phosphoglycolate-terminated DNA double-strand breaks

    DNA Repair (Amst.)

    (2009)
  • V. Bandaru

    A novel human DNA glycosylase that removes oxidative DNA damage and is homologous to Escherichia coli endonuclease VIII

    DNA Repair (Amst.)

    (2002)
  • A. Das

    NEIL2-initiated, APE-independent repair of oxidized bases in DNA: evidence for a repair complex in human cells

    DNA Repair (Amst.)

    (2006)
  • M. Audebert

    Involvement of polynucleotide kinase in a poly(ADP-ribose) polymerase-1-dependent DNA double-strand breaks rejoining pathway

    J. Mol. Biol.

    (2006)
  • R.S. Mani

    Dual modes of interaction between XRCC4 and polynucleotide kinase/phosphatase: implications for nonhomologous end joining

    J. Biol. Chem.

    (2010)
  • K.V. Inamdar

    Conversion of phosphoglycolate to phosphate termini on 3′ overhangs of DNA double strand breaks by the human tyrosyl-DNA phosphodiesterase hTdp1

    J. Biol. Chem.

    (2002)
  • M. O’Driscoll

    DNA ligase IV mutations identified in patients exhibiting developmental delay and immunodeficiency

    Mol. Cell

    (2001)
  • J.R. Whiteside

    Cadmium and copper inhibit both DNA repair activities of polynucleotide kinase

    DNA Repair (Amst.)

    (2010)
  • G.K. Freschauf

    Mechanism of action of an imidopiperidine inhibitor of human polynucleotide kinase/phosphatase

    J. Biol. Chem.

    (2010)
  • W.D. Henner

    gamma Ray induced deoxyribonucleic acid strand breaks. 3′ Glycolate termini

    J. Biol. Chem.

    (1983)
  • J.F. Ward

    DNA damage produced by ionizing radiation in mammalian cells: identities, mechanisms of formation, and reparability

    Prog. Nucleic Acid Res. Mol. Biol.

    (1988)
  • L.F. Povirk

    DNA damage and mutagenesis by radiomimetic DNA-cleaving agents: bleomycin, neocarzinostatin and other enediynes

    Mutat. Res.

    (1996)
  • T.K. Hazra

    Identification and characterization of a novel human DNA glycosylase for repair of cytosine-derived lesions

    J. Biol. Chem.

    (2002)
  • T.A. Rosenquist

    The novel DNA glycosylase, NEIL1, protects mammalian cells from radiation-mediated cell death

    DNA Repair (Amst.)

    (2003)
  • A. Katafuchi

    Differential specificity of human and Escherichia coli endonuclease III and VIII homologues for oxidative base lesions

    J. Biol. Chem.

    (2004)
  • J.H. Hoeijmakers

    DNA damage, aging, and cancer

    N. Engl. J. Med.

    (2009)
  • L.A. Loeb et al.

    Advances in chemical carcinogenesis: a historical review and prospective

    Cancer Res.

    (2008)
  • P.J. McKinnon

    DNA repair deficiency and neurological disease

    Nat. Rev. Neurosci.

    (2009)
  • E.C.W. Friedberg

    DNA Repair and Mutagenesis

    (2006)
  • Cited by (0)

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