title: The role of DNA damage response pathways in chromosome fragility in Fragile X syndrome.
abstract: FRAXA is one of a number of fragile sites in human chromosomes that are induced by agents like fluorodeoxyuridine (FdU) that affect intracellular thymidylate levels. FRAXA coincides with a >200 CGG*CCG repeat tract in the 5' UTR of the FMR1 gene, and alleles prone to fragility are associated with Fragile X (FX) syndrome, one of the leading genetic causes of intellectual disability. Using siRNA depletion, we show that ATR is involved in protecting the genome against FdU-induced chromosome fragility. We also show that FdU increases the number of gamma-H2AX foci seen in both normal and patient cells and increases the frequency with which the FMR1 gene colocalizes with these foci in patient cells. In the presence of FdU and KU55933, an ATM inhibitor, the incidence of chromosome fragility is reduced, suggesting that ATM contributes to FdU-induced chromosome fragility. Since both ATR and ATM are involved in preventing aphidicolin-sensitive fragile sites, our data suggest that the lesions responsible for aphidicolin-induced and FdU-induced fragile sites differ. FRAXA also displays a second form of chromosome fragility in absence of FdU, which our data suggest is normally prevented by an ATM-dependent process.
authors.affiliation: Section on Gene Structure and Disease, Laboratory of Molecular and Cellular Biology, National Institute of Diabetes, Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-0830, USA.
authors.forename: Daman
authors.initials: D
authors.lastname: Kumari
authors.forename: Valentina
authors.initials: V
authors.lastname: Somma
authors.forename: Asako J
authors.initials: AJ
authors.lastname: Nakamura
authors.forename: William M
authors.initials: WM
authors.lastname: Bonner
authors.forename: Ettoré
authors.initials: E
authors.lastname: D'Ambrosio
authors.forename: Karen
authors.initials: K
authors.lastname: Usdin
mesh_terms: D016590:Aphidicolin / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D019457:Chromosome Breakage; D043283:Chromosome Fragile Sites; D002873:Chromosome Fragility; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005467:Floxuridine / Q000494:pharmacology; D051860:Fragile X Messenger Ribonucleoprotein 1 / Q000235:genetics; D005600:Fragile X Syndrome / Q000201:enzymology / Q000235:genetics*; D055785:Gene Knockdown Techniques; D006657:Histones / Q000032:analysis; D006801:Humans; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011753:Pyrones / Q000494:pharmacology; D019311:Staurosporine / Q000031:analogs & derivatives / Q000494:pharmacology; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D016590:Aphidicolin; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005467:Floxuridine; D051860:Fragile X Messenger Ribonucleoprotein 1; D006657:Histones; D009025:Morpholines; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011753:Pyrones; D019311:Staurosporine; D025521:Tumor Suppressor Proteins; C495818:2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one; C497683:FMR1 protein, human; C468783:H2AX protein, human; C054852:7-hydroxystaurosporine; C576324:ATM protein, human; C576597:ATR protein, human