Volume 30, No 11, Nov 2020

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 30 Issue 11, November 2020: 997-1008   |  Open Access

ORIGINAL ARTICLES

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

Morgane Macheret¹ , Rahul Bhowmick² , Katarzyna Sobkowiak¹ , Laura Padayachy² , Jonathan Mailler¹ , Ian D. Hickson^2,* , Thanos D. Halazonetis^1,*

¹Department of Molecular Biology, University of Geneva, 1205 Geneva, Switzerland
²Center for Chromosome Stability and Center for Healthy Aging, Department of Cellular and Molecular Medicine, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
^†These authors contributed equally: Morgane Macheret, Rahul Bhowmick, Katarzyna Sobkowiak
Correspondence: Ian D. Hickson(iandh@sund.ku.dk)Thanos D. Halazonetis(thanos.halazonetis@unige.ch)

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.

https://doi.org/10.1038/s41422-020-0358-x

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