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Study reports a novel missense variant c.1133A>C (p.Lys378Thr) on the 13th exon of PNKP gene identified by whole exome sequencing in an Iranian multi-affected family with microcephaly, seizures and developmental delay disorder.
This study found that an XRCC1 fragment, comprising residues 166-436, binds tightly to PNKP and DNA and efficiently activates PNKP's kinase activity.
Despite presence of an alternative 3'-phosphatase, loss of PNKP significantly sensitizes cells to 3'-phosphate-terminated DSBs, due to a 3'-dephosphorylation defect.
PNKP mutation in two siblings is associated with progressive ataxia, abnormal saccades, sensorimotor neuropathy and dystonia consistent with ataxia with oculomotor apraxia disorders.
we have identified a mutation in PNKP, leading to a phenotype of microcephaly with primordial dwarfism.
XRCC1 and PNKP interact via a high-affinity phosphorylation-dependent interaction site in XRCC1 and a forkhead-associated domain in PNKP. Data suggest a second PNKP interaction site in XRCC1 that binds PNKP with lower affinity and independently of XRCC1 phosphorylation. (XRCC1 = X-ray repair cross complementing protein 1; PNKP = polynucleotide kinase 3'-phosphatase)
In a recombinant PNKP-XRCC4-LigIV complex, stable binding of PNKP requires XRCC4 phosphorylation. Only one PNKP protomer binds per XRCC4 dimer. Both the PNKP FHA and catalytic domains contact the XRCC4 coiled-coil and LigIV BRCT repeats. A surface on the PNKP phosphatase domain may contact XRCC4-LigIV. A mutation on this surface (E326K) impairs PNKP recruitment to damaged DNA and causes microcephaly with seizures.
Mutations in TDP1 and APTX have been linked to Spinocerebellar ataxia with axonal neuropathy (SCAN1) and Ataxia-ocular motor apraxia 1 (AOA1), respectively, while mutations in PNKP are considered to be responsible for Microcephaly with seizures (MCSZ) and Ataxia-ocular motor apraxia 4 (AOA4).
the role for PNKP in maintaining brain function and how perturbation in its activity can account for the varied pathology of neurodegeneration or microcephaly present in microcephaly with seizures and ataxia with oculomotor apraxia 4 respectively.
In 11 Portuguese patients, PNKP mutations cause ataxia with oculomotor apraxia type 4.
Here we report that purified wild-type (WT) ATXN3 stimulates, and by contrast the mutant form specifically inhibits, PNKP's 3' phosphatase activity in vitro. ATXN3-deficient cells also show decreased PNKP activity
We now report that the mutant ATXN3 protein interacts with and inactivates PNKP (polynucleotide kinase 3'-phosphatase), an essential DNA strand break repair enzyme
We identified homozygous or compound-heterozygous PNKP mutations in eight of the nine Portuguese families we studied, suggesting that, in Portugal, mutations in PNKP are the most frequent cause of ataxia with oculomotor apraxia.
we show that modest inhibition of PNKP in a PTEN knockout background enhances cellular radiosensitivity, suggesting that such a "synthetic sickness" approach involving the combination of PNKP inhibition with radiotherapy
Mutations in PNKP have previously been associated with a syndrome of microcephaly, seizures and developmental delay (MIM 613402), and is now associated with a neurodegenerative disorder.
the interaction between PNKP and XRCC1 has roles in the retention of XRCC1 at DNA damage sites and in DNA alkylation damage repair
The data suggest that all four known mutations associated with microcephaly, seizures and developmental delay reduce the cellular stability and level of PNKP protein, with three mutations likely ablating cellular DNA 5'-kinase activity and all of the mutations greatly reducing cellular DNA 3'-phosphatase activity.
the critical role of NEIL2 and PNKP in maintenance of the mammalian mitochondrial genome.
PNKP distorts target DNA structures to access damaged substrate DNA ends, thus providing a molecular mechanism for the involvement of PNKP in the repair of both single- and double-strand breaks.
Results reveal that ionizing radiation-induced phosphorylation of PNKP by ATM and DNA-PK regulates PNKP function at DNA double strand breaks.
Repair independent of the well documented XRCC1-PNKP interaction was studied. XRCC1 can mediate repair of strand breaks without PNKP binding.
The work indicates that the phosphatase domain of Pnkp binds 3'-phosphorylated single-stranded DNAs in a manner that is highly dependent on the presence of the 3'-phosphate.
Directed postnatal neural inactivation of PNKP affected specific subpopulations including oligodendrocytes, indicating a broad requirement for genome maintenance, both during and after neurogenesis.
Structure of dsDNA bound to PNK 5'-kinase domain reveals DNA bending facilitating recognition of DNA ends in the context of single-strand/double-strand breaks, suggesting close functional cooperation in between the kinase/phosphatase active sites.
analysis of the molecular architecture of polynucleotide kinase
This locus represents a gene involved in DNA repair. In response to ionizing radiation or oxidative damage, the protein encoded by this locus catalyzes 5' phosphorylation and 3' dephosphorylation of nucleic acids. Mutations at this locus have been associated with microcephaly, seizures, and developmental delay.
, Homo sapiens polynucleotide kinase 3'-phosphatase (PNKP)
, bifunctional polynucleotide phosphatase/kinase
, polynucleotide kinase 3'-phosphatase
, polynucleotide kinase-3'-phosphatase