title: Defective DNA repair and increased chromatin binding of DNA repair factors in Down syndrome fibroblasts.
abstract: Down syndrome (DS) is characterized by genetic instability, neurodegeneration, and premature aging. However, the molecular mechanisms leading to this phenotype are not yet well understood. Here, we report that DS fibroblasts from both fetal and adult donors show the presence of oxidative DNA base damage, such as dihydro-8-oxoguanine (8-oxodG), and activation of a DNA damage response (DDR), already during unperturbed growth conditions. DDR with checkpoint activation was indicated by histone H2AX and Chk2 protein phosphorylation, and by increased p53 protein levels. In addition, both fetal and adult DS fibroblasts were more sensitive to oxidative DNA damage induced by potassium bromate, and were defective in the removal of 8-oxodG, as compared with age-matched cells from control healthy donors. The analysis of core proteins participating in base excision repair (BER), such as XRCC1 and DNA polymerase β, showed that higher amounts of these factors were bound to chromatin in DS than in control cells, even in the absence of DNA damage. These findings occurred in concomitance with increased levels of phosphorylated XRCC1 detected in DS cells. These results indicate that DS cells exhibit a BER deficiency, which is associated with prolonged chromatin association of core BER factors.
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy. Electronic address: necchi.d@unipv.it.
authors.forename: Daniela
authors.initials: D
authors.lastname: Necchi
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Pinto
authors.affiliation: Institute of Molecular Genetics of the National Research Council (CNR), 27100 Pavia, Italy.
authors.forename: Micol
authors.initials: M
authors.lastname: Tillhon
authors.affiliation: Institute of Molecular Genetics of the National Research Council (CNR), 27100 Pavia, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Dutto
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
authors.forename: Melania Maria
authors.initials: MM
authors.lastname: Serafini
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Lanni
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Govoni
authors.affiliation: Department of Drug Sciences, University of Pavia, 27100 Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Racchi
authors.affiliation: Institute of Molecular Genetics of the National Research Council (CNR), 27100 Pavia, Italy. Electronic address: prosperi@igm.cnr.it.
authors.forename: Ennio
authors.initials: E
authors.lastname: Prosperi
mesh_terms: D000328:Adult; D002478:Cells, Cultured; D064447:Checkpoint Kinase 2 / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004314:Down Syndrome / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D005260:Female; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D006147:Guanine / Q000031:analogs & derivatives / Q000378:metabolism; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D010766:Phosphorylation / Q000235:genetics; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D000076105:X-ray Repair Cross Complementing Protein 1
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D000076105:X-ray Repair Cross Complementing Protein 1; C000619371:XRCC1 protein, human; C024829:8-hydroxyguanine; D006147:Guanine; D064447:Checkpoint Kinase 2; C578634:CHEK2 protein, human
keywords: Base excision repair; Chromatin recruitment; DNA damage response; Down syndrome; Oxidative DNA damage