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bioRxiv · 10.1101/2023.08.16.553614

DONSON is required for CMG helicase assembly in the mammalian cell cycle

Labib, K.·Evrin, C.·Alvarez, V.·Ainsworth, J.·Fujisawa, R.·Alabert, C.
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Abstract

DONSON is one of 13 genes mutated in a form of primordial microcephalic dwarfism known as Meier-Gorlin Syndrome. The other 12 encode components of the CDC45-MCM-GINS helicase, around which the eukaryotic replisome forms, or are factors required for helicase assembly during DNA replication initiation. A role for DONSON in CDC45-MCM-GINS assembly was unanticipated, since DNA replication initiation can be reconstituted in vitro with purified proteins from budding yeast, which lacks DONSON. Using mouse embryonic stem cells as a model for the mammalian helicase, we show that DONSON binds directly but transiently to CDC45-MCM-GINS during S-phase and is essential for chromosome duplication. Rapid depletion of DONSON leads to the disappearance of the CDC45-MCM-GINS helicase from S-phase cells and our data indicate that DONSON is dispensable for loading of the MCM2-7 helicase core onto chromatin during G1-phase, but instead is essential for CDC45-MCM-GINS assembly during S-phase. These data identify DONSON as a missing link in our understanding of mammalian chromosome duplication and provide a molecular explanation for why mutations in human DONSON are associated with Meier-Gorlin syndrome.

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Labib, K., Evrin, C., Alvarez, V., Ainsworth, J., Fujisawa, R., Alabert, C.. 2023-08-17. DONSON is required for CMG helicase assembly in the mammalian cell cycle. https://doi.org/10.1101/2023.08.16.553614

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