RESUMEN
Pourfour du Petit Syndrome (PdPS) is characterized by signs of oculosympathetic hyperactivity caused by irritation in the oculosympathetic pathway and shares etiologies with Horner Syndrome. We present the case of a 64-year-old woman with Pourfour du Petit syndrome due to compression of the second-order cervical sympathetic chain neuron from a dominant and prominent right internal jugular vein compensatory for contralateral agenesis. Internal jugular vein agenesis is a rare developmental vascular anomaly and is asymptomatic in the majority of patients with this condition.
RESUMEN
Non-homologous end joining (NHEJ) repairs DNA double strand breaks in non-cycling eukaryotic cells. NHEJ relies on polynucleotide kinase/phosphatase (PNKP), which generates 5Î-phosphate/3Î-hydroxyl DNA termini that are critical for ligation by the NHEJ DNA ligase, LigIV. PNKP and LigIV require the NHEJ scaffolding protein, XRCC4. The PNKP FHA domain binds to the CK2-phosphorylated XRCC4 C-terminal tail, while LigIV uses its tandem BRCT repeats to bind the XRCC4 coiled-coil. Yet, the assembled PNKP-XRCC4-LigIV complex remains uncharacterized. Here, we report purification and characterization of a recombinant PNKP-XRCC4-LigIV complex. We show that the stable binding of PNKP in this complex requires XRCC4 phosphorylation and that only one PNKP protomer binds per XRCC4 dimer. Small angle X-ray scattering (SAXS) reveals a flexible multi-state complex that suggests that both the PNKP FHA and catalytic domains contact the XRCC4 coiled-coil and LigIV BRCT repeats. Hydrogen-deuterium exchange indicates protection of a surface on the PNKP phosphatase domain that may contact XRCC4-LigIV. A mutation on this surface (E326K) causes the hereditary neuro-developmental disorder, MCSZ. This mutation impairs PNKP recruitment to damaged DNA in human cells and provides a possible disease mechanism. Together, this work unveils multipoint contacts between PNKP and XRCC4-LigIV that regulate PNKP recruitment and activity within NHEJ.
Asunto(s)
Reparación del ADN por Unión de Extremidades/fisiología , ADN Ligasa (ATP)/fisiología , Enzimas Reparadoras del ADN/fisiología , Proteínas de Unión al ADN/fisiología , Fosfotransferasas (Aceptor de Grupo Alcohol)/fisiología , Dominio Catalítico , Daño del ADN , ADN Ligasa (ATP)/química , Enzimas Reparadoras del ADN/química , Enzimas Reparadoras del ADN/deficiencia , Enzimas Reparadoras del ADN/genética , Proteínas de Unión al ADN/química , Deuterio/metabolismo , Discapacidades del Desarrollo/genética , Humanos , Espectrometría de Masas , Microcefalia/genética , Modelos Moleculares , Complejos Multiproteicos , Mutación Missense , Fosforilación , Fosfotransferasas (Aceptor de Grupo Alcohol)/química , Fosfotransferasas (Aceptor de Grupo Alcohol)/deficiencia , Fosfotransferasas (Aceptor de Grupo Alcohol)/genética , Mutación Puntual , Unión Proteica , Conformación Proteica , Mapeo de Interacción de Proteínas , Procesamiento Proteico-Postraduccional , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Dispersión del Ángulo Pequeño , Convulsiones/genética , Síndrome , Difracción de Rayos XRESUMEN
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.
