Bernard S Lopez
Institut Gustave Roussy, France
University of Grenoble, France
Replication stress is an endogenous stress that can be at the origin of senescence or tumor initiation. Replication stress generates mitosis defects including anaphases bridges, expression of common fragile sites, extra-centrosomes and multipolar segregations. All these troubles generate uneven chromosome segregation and aneuploidy. This suggests that DNA damages arising from replication should reach mitosis. To test this hypothesis wen checked the accumulation of foci of RPA, which recognize single-stranded DNA, in cells in late G2, following a low or endogenous replication stress. Cells treated with low doses of hydroxyurea (HU, 10 μM) or untreated cells defective for homologous recombination (HR); which plays a pivotal role in the resumption of arrested replication forks, both experience an increase in the number of RPA foci, in late G2 phase. These foci do not co-localize with progressing replication forks completing replication, and thus should correspond to spontaneous replication fork arrest. ChIP-seq analysis with RPA antibodies in G2 phase reveals two types of enrichment efficiency. Highly enriched sequences (more than 400) do not contained fragile sites and correspond to early replicating sequences. Interestingly many of these sequences correspond to transcription starting sites (TSS), revealing thus the conflict between replication and transcription. Among the genes involved a set of 10 genes involved in DNA damage response and cell cycle checkpoint have been selected and specific chromatin-IP experiment confirmed the binding of RPA after HU. Therefore promoters of genes controlling genome stability are hot spots of endogenous/low replication stress favoring damaged cells to escape to cell surveillance. Therefore should amplify genome instability.
Bernard S Lopez has completed his PhD from the University of Lyon I and Post-doctoral studies from Curie Institute (Paris), followed by a sabbatical from and Brandeis University USA. He is a Research Director at CNRS. He has published more than 70 papers in reputed journals and has been serving as a Scientific Advisor of many organizations.
