title: Pyrimidine Pool Disequilibrium Induced by a Cytidine Deaminase Deficiency Inhibits PARP-1 Activity, Leading to the Under Replication of DNA.
abstract: Genome stability is jeopardized by imbalances of the dNTP pool; such imbalances affect the rate of fork progression. For example, cytidine deaminase (CDA) deficiency leads to an excess of dCTP, slowing the replication fork. We describe here a novel mechanism by which pyrimidine pool disequilibrium compromises the completion of replication and chromosome segregation: the intracellular accumulation of dCTP inhibits PARP-1 activity. CDA deficiency results in incomplete DNA replication when cells enter mitosis, leading to the formation of ultrafine anaphase bridges between sister-chromatids at "difficult-to-replicate" sites such as centromeres and fragile sites. Using molecular combing, electron microscopy and a sensitive assay involving cell imaging to quantify steady-state PAR levels, we found that DNA replication was unsuccessful due to the partial inhibition of basal PARP-1 activity, rather than slower fork speed. The stimulation of PARP-1 activity in CDA-deficient cells restores replication and, thus, chromosome segregation. Moreover, increasing intracellular dCTP levels generates under-replication-induced sister-chromatid bridges as efficiently as PARP-1 knockdown. These results have direct implications for Bloom syndrome (BS), a rare genetic disease combining susceptibility to cancer and genomic instability. BS results from mutation of the BLM gene, encoding BLM, a RecQ 3'-5' DNA helicase, a deficiency of which leads to CDA downregulation. BS cells thus have a CDA defect, resulting in a high frequency of ultrafine anaphase bridges due entirely to dCTP-dependent PARP-1 inhibition and independent of BLM status. Our study describes previously unknown pathological consequences of the distortion of dNTP pools and reveals an unexpected role for PARP-1 in preventing DNA under-replication and chromosome segregation defects.
authors.affiliation: Institut Curie, Centre de Recherche, Orsay, France; CNRS UMR 3348, Stress Génotoxiques et Cancer, Centre Universitaire, Orsay, France.
authors.forename: Simon
authors.initials: S
authors.lastname: Gemble
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
authors.forename: Akshay
authors.initials: A
authors.lastname: Ahuja
authors.affiliation: Institut Curie, Centre de Recherche, Orsay, France; CNRS UMR 3348, Stress Génotoxiques et Cancer, Centre Universitaire, Orsay, France.
authors.forename: Géraldine
authors.initials: G
authors.lastname: Buhagiar-Labarchède
authors.affiliation: Institut Curie, Centre de Recherche, Orsay, France; CNRS UMR 3348, Stress Génotoxiques et Cancer, Centre Universitaire, Orsay, France.
authors.forename: Rosine
authors.initials: R
authors.lastname: Onclercq-Delic
authors.affiliation: Université Paris Diderot, Sorbonne Paris Cité, Unité de Biologie Fonctionnelle et Adaptative (BFA) UMR 8251 CNRS, Plateforme Bioprofiler Bâtiment Buffon, 346A Case 7073, Paris, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Dairou
authors.affiliation: CEA, DSV, iMETI, SEPIA, Fontenay-aux-Roses Cedex, France.
authors.forename: Denis S F
authors.initials: DS
authors.lastname: Biard
authors.affiliation: Institut Curie, Centre de Recherche, Orsay, France; CNRS UMR 3348, Stress Génotoxiques et Cancer, Centre Universitaire, Orsay, France.
authors.forename: Sarah
authors.initials: S
authors.lastname: Lambert
authors.affiliation: Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
authors.forename: Massimo
authors.initials: M
authors.lastname: Lopes
authors.affiliation: Institut Curie, Centre de Recherche, Orsay, France; CNRS UMR 3348, Stress Génotoxiques et Cancer, Centre Universitaire, Orsay, France.
authors.forename: Mounira
authors.initials: M
authors.lastname: Amor-Guéret
mesh_terms: D001816:Bloom Syndrome / Q000235:genetics* / Q000473:pathology; D002460:Cell Line; D002503:Centromere / Q000235:genetics; D043283:Chromosome Fragile Sites / Q000235:genetics; D020090:Chromosome Segregation / Q000235:genetics; D003564:Cytidine Deaminase / Q000172:deficiency / Q000235:genetics*; D004261:DNA Replication / Q000235:genetics; D042822:Genomic Instability; D006801:Humans; D008938:Mitosis / Q000235:genetics; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000096:biosynthesis / Q000235:genetics*; D011743:Pyrimidines / Q000378:metabolism*; D053484:RecQ Helicases / Q000235:genetics; D012854:Sister Chromatid Exchange / Q000235:genetics
chemical_list: D011743:Pyrimidines; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D003564:Cytidine Deaminase; C097151:Bloom syndrome protein; D053484:RecQ Helicases; C030986:pyrimidine