FANCD1/BRCA2 Plays Predominant Role in the Repair of DNA Damage Induced by ACNU or TMZ

Nimustine (ACNU) and temozolomide (TMZ) are DNA alkylating agents which are commonly used in chemotherapy for glioblastomas. ACNU is a DNA cross-linking agent and TMZ is a methylating agent. The therapeutic efficacy of these agents is limited by the development of resistance. In this work, the role of the Fanconi anemia (FA) repair pathway for DNA damage induced by ACNU or TMZ was examined. Cultured mouse embryonic fibroblasts were used: FANCA−/−, FANCC−/−, FANCA−/−C−/−, FANCD2−/− cells and their parental cells, and Chinese hamster ovary and lung fibroblast cells were used: FANCD1/BRCA2mt, FANCG−/− and their parental cells. Cell survival was examined after a 3 h ACNU or TMZ treatment by using colony formation assays. All FA repair pathways were involved in ACNU-induced DNA damage. However, FANCG and FANCD1/BRCA2 played notably important roles in the repair of TMZ-induced DNA damage. The most effective molecular target correlating with cellular sensitivity to both ACNU and TMZ was FANCD1/BRCA2. In addition, it was found that FANCD1/BRCA2 small interference RNA efficiently enhanced cellular sensitivity toward ACNU and TMZ in human glioblastoma A172 cells. These findings suggest that the down-regulation of FANCD1/BRCA2 might be an effective strategy to increase cellular chemo-sensitization towards ACNU and TMZ

Warsaw Breakage Syndrome, a Cohesinopathy Associated with Mutations in the XPD Helicase Family Member DDX11/ChlR1

The iron-sulfur-containing DNA helicases XPD, FANCJ, DDX11, and RTEL represent a small subclass of superfamily 2 helicases. XPD and FANCJ have been connected to the genetic instability syndromes xeroderma pigmentosum and Fanconi anemia. Here, we report a human individual with biallelic mutations in DDX11. Defective DDX11 is associated with a unique cellular phenotype in which features of Fanconi anemia (drug-induced chromosomal breakage) and Roberts syndrome (sister chromatid cohesion defects) coexist. The DDX11-deficient patient represents another cohesinopathy, besides Cornelia de Lange syndrome and Roberts syndrome, and shows that DDX11 functions at the interface between DNA repair and sister chromatid cohesion

siRNA silencing of <i>FANCD1/BRCA2</i> in glioblastoma A172 cells after ACNU and TMZ treatments.

<p><b>a</b>, expression analysis of FANCD1/BRCA2 in cells transfected with siRNA for human <i>FANCD1/BRCA2</i> or the negative control siRNA using Western blots. Actin was used as a loading control, and the relative ratios of protein were normalized using actin levels. <b>b</b>, effect of siRNA silencing of <i>FANCD1/BRCA2</i> on cellular sensitivity to ACNU and TMZ. <b>c</b>, effect of siRNA silencing of <i>FANCD1/BRCA2</i> on cell growth after ACNU or TMZ treatment. Open columns, negative control siRNA; closed columns, <i>FANCD1/BRCA2</i> siRNA. Columns show the mean of three independent experiments; the bars indicate the SD. An asterisk (*) indicates significant difference (<i>P</i><0.05). Two asterisks (**), <i>P</i><0.01; three asterisks (***), <i>P</i><0.001.</p