High-resolution mapping of mitotic DNA synthesis regions and common fragile sites in the human genome through direct sequencing

• Published in: Cell research Vol. 30; no. 11; pp. 997 - 1008
• Main Authors: Macheret, Morgane, Bhowmick, Rahul, Sobkowiak, Katarzyna, Padayachy, Laura, Mailler, Jonathan, Hickson, Ian D., Halazonetis, Thanos D.
• Format: Journal Article
• Language: English
• Published: Singapore Springer Singapore 01-11-2020; Nature Publishing Group
• Subjects: 45; 631/337/1427; 631/67; Aphidicolin; Biomedical and Life Sciences; Cancer; Cell Biology; Cell Line, Tumor; Chromosome Breakage; Chromosome Fragile Sites - genetics; Deoxyribonucleic acid; DNA; DNA - biosynthesis; DNA polymerase; DNA repair; DNA Replication Timing - genetics; DNA sequencing; DNA-directed DNA polymerase; Fragile sites; Gene mapping; Genome, Human; Genomes; Genomic Instability; Genomics; High resolution; Humans; Life Sciences; Mitosis; Mitosis - genetics; Molecular Sequence Annotation; Neoplasms - genetics; Replication; Replication forks; Replication Origin - genetics; S phase; Sequence Analysis, DNA; Synthesis
• ISSN: 1001-0602; 1748-7838
• DOI: 10.1038/s41422-020-0358-x

DNA replication stress, a feature of human cancers, often leads to instability at specific genomic loci, such as the common fragile sites (CFSs). Cells experiencing DNA replication stress may also exhibit mitotic DNA synthesis (MiDAS). To understand the physiological function of MiDAS and its relationship to CFSs, we mapped, at high resolution, the genomic sites of MiDAS in cells treated with the DNA polymerase inhibitor aphidicolin. Sites of MiDAS were evident as well-defined peaks that were largely conserved between cell lines and encompassed all known CFSs. The MiDAS peaks mapped within large, transcribed, origin-poor genomic regions. In cells that had been treated with aphidicolin, these regions remained unreplicated even in late S phase; MiDAS then served to complete their replication after the cells entered mitosis. Interestingly, leading and lagging strand synthesis were uncoupled in MiDAS, consistent with MiDAS being a form of break-induced replication, a repair mechanism for collapsed DNA replication forks. Our results provide a better understanding of the mechanisms leading to genomic instability at CFSs and in cancer cells.