DNA synthesis by Pol η promotes fragile site stability by preventing under-replicated DNA in mitosis

• Published in: The Journal of cell biology 2013-04, Vol.201 (3), p.395-408
• Main Authors: Bergoglio, Valérie, Boyer, Anne-Sophie, Walsh, Erin, Naim, Valeria, Legube, Gaëlle, Lee, Marietta Y W T, Rey, Laurie, Rosselli, Filippo, Cazaux, Christophe, Eckert, Kristin A, Hoffmann, Jean-Sébastien
• Format: Article
• Language: English
• Subjects: Cell Line, Tumor; Cell Nucleus - enzymology; Chromosome Fragile Sites; Chromosome Fragility; DNA Replication; DNA, B-Form - genetics; DNA-Directed DNA Polymerase - genetics; DNA-Directed DNA Polymerase - metabolism; DNA-Directed DNA Polymerase - physiology; Homologous Recombination; Humans; Inverted Repeat Sequences; Life Sciences; Mitosis; Protein Binding; S Phase Cell Cycle Checkpoints; Stress, Physiological
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.201207066

Human DNA polymerase η (Pol η) is best known for its role in responding to UV irradiation-induced genome damage. We have recently observed that Pol η is also required for the stability of common fragile sites (CFSs), whose rearrangements are considered a driving force of oncogenesis. Here, we explored the molecular mechanisms underlying this newly identified role. We demonstrated that Pol η accumulated at CFSs upon partial replication stress and could efficiently replicate non-B DNA sequences within CFSs. Pol η deficiency led to persistence of checkpoint-blind under-replicated CFS regions in mitosis, detectable as FANCD2-associated chromosomal sites that were transmitted to daughter cells in 53BP1-shielded nuclear bodies. Expression of a catalytically inactive mutant of Pol η increased replication fork stalling and activated the replication checkpoint. These data are consistent with the requirement of Pol η-dependent DNA synthesis during S phase at replication forks stalled in CFS regions to suppress CFS instability by preventing checkpoint-blind under-replicated DNA in mitosis.