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YAP as a Regulator of DNA Replication Timing

Abstract : Stemness could be defined as a state in which a cell is able to self-renew and/or to differentiate after cell division. Before this happens, exhaustive duplication of the genome free of errors must occur in order to avoid deleterious mutations, a hallmark of cancer. Thus, DNA replication is particularly important to stem cells because of their continuous division capacities. Regarding DNA replication in eukaryotes, it was discovered that segments of chromosomes close in space, replicate in a coordinated manner during S phase, a process called replication timing. Moreover, major changes in replication timing correlate with cell differentiation, 3D chromatin architecture and transcription. However, the molecules that govern its regulation are poorly understood. Previously, my laboratory found that YAP, the downstream effector of the Hippo pathway, regulates S phase progression of retinal stem cells in Xenopus laevis. To test YAP function in the direct control of replication timing, we took advantage of the powerful in vitro DNA replication system of X. laevis egg extracts. Briefly, we discovered that YAP is recruited to replicating chromatin dependently of origin licensing. In addition, YAP depleted extracts showed increased DNA synthesis and origin activation; revealing that YAP normal function is to slow-down replication by limiting origin firing. Interestingly, we found Rif1, a major regulator of replication timing, as a novel partner of YAP. In vivo, Rif1 expression overlaps that of Yap within the stem cell compartment of the Xenopus retina. Knockdown of Rif1 leaded to a small-eye phenotype and alterations in replication foci of retinal stem cells, resembling the effect observed in YAP deficient cells. Finally, early-embryonic depletion of both molecules resulted in a strikingly acceleration of cell division.Altogether, our findings unveil YAP implication in the regulation of replication dynamis and show Rif1 as a novel partner. Further investigation to analyze this interaction would help us to understand the biological relevance in the control of replication timing and whether it could be used as a target in regenerative medicine.
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  • HAL Id : tel-02989691, version 1

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Rodrigo Meléndez García. YAP as a Regulator of DNA Replication Timing. Molecular biology. Université Paris-Saclay, 2020. English. ⟨NNT : 2020UPASL014⟩. ⟨tel-02989691⟩

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