Mitotic DNA Synthesis in Untransformed Human Cells Preserves Common Fragile Site Stability via a FANCD2-Driven Mechanism That Requires HELQ

Emma L. Traband, Sarah R. Hammerlund, Mohammad Shameem, Ananya Narayan, Sanjiv Ramana, Anika Tella, Alexandra Sobeck, Naoko Shima

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Faithful genome duplication is a challenging task for dividing mammalian cells, particularly under replication stress where timely resolution of late replication intermediates (LRIs) becomes crucial prior to cell division. In human cancer cells, mitotic DNA repair synthesis (MiDAS) is described as a final mechanism for the resolution of LRIs to avoid lethal chromosome mis-segregation. RAD52-driven MiDAS achieves this mission in part by generating gaps/breaks on metaphase chromosomes, which preferentially occur at common fragile sites (CFS). We previously demonstrated that a MiDAS mechanism also exists in untransformed and primary human cells, which is RAD52 independent but requires FANCD2. However, the properties of this form of MiDAS are not well understood. Here, we report that FANCD2-driven MiDAS in untransformed human cells: 1) requires a prerequisite step of FANCD2 mono-ubiquitination by a subset of Fanconi anemia (FA) proteins, 2) primarily acts to preserve CFS stability but not to prevent chromosome mis-segregation, and 3) depends on HELQ, which potentially functions at an early step. Hence, FANCD2-driven MiDAS in untransformed cells is built to protect CFS stability, whereas RAD52-driven MiDAS in cancer cells is likely adapted to prevent chromosome mis-segregation at the cost of CFS expression. Notably, we also identified a novel form of MiDAS, which surfaces to function when FANCD2 is absent in untransformed cells. Our findings substantiate the complex nature of MiDAS and a link between its deficiencies and the pathogenesis of FA, a human genetic disease.

Original languageEnglish (US)
Article number168294
JournalJournal of Molecular Biology
Volume435
Issue number22
DOIs
StatePublished - Nov 15 2023

Bibliographical note

Publisher Copyright:
© 2023 The Author(s)

Keywords

  • Fanconi anemia
  • HELQ
  • common fragile sites
  • replication stress
  • untransformed human cells

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