Rapid DNA replication origin licensing protects stem cell pluripotency
Abstract
Complete and robust human genome duplication requires loading MCM helicase complexes at many DNA replication origins, an essential process termed origin licensing. Licensing is restricted to G1 phase of the cell cycle, but G1 length varies widely among cell types. Using quantitative single cell analyses we found that pluripotent stem cells with naturally short G1 phases load MCM much faster than their isogenic differentiated counterparts with long G1 phases. During the earliest stages of differentiation towards all lineages, MCM loading slows concurrently with G1 lengthening, revealing developmental control of MCM loading. In contrast, ectopic Cyclin E overproduction uncouples short G1 from fast MCM loading. Rapid licensing in stem cells is caused by accumulation of the MCM loading protein, Cdt1. Prematurely slowing MCM loading in pluripotent cells not only lengthens G1 but also accelerates differentiation. Thus, rapid origin licensing is an intrinsic characteristic of stem cells that contributes to pluripotency maintenance.
Article and author information
Author details
Funding
National Institutes of Health (Research Grant GM074917)
- Anja-Katrin Bielinsky
National Science Foundation (Graduate Student Research Fellowship DGE1144081)
- Jacob Peter Matson
W. M. Keck Foundation (Research Grant)
- Jeremy E Purvis
- Jeanette Gowen Cook
National Institutes of Health (Training Grant T32CA009138)
- Ryan M Baxley
National Institutes of Health (Research Grant GM083024)
- Jeanette Gowen Cook
National Institutes of Health (Research Grant DP2HD091800)
- Jeremy E Purvis
National Institutes of Health (Research Grant GM102413)
- Jeanette Gowen Cook
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Bruce Stillman, Cold Spring Harbor Laboratory, United States
Version history
- Received: July 17, 2017
- Accepted: November 16, 2017
- Accepted Manuscript published: November 17, 2017 (version 1)
- Version of Record published: December 7, 2017 (version 2)
- Version of Record updated: June 5, 2019 (version 3)
Copyright
© 2017, Matson et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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Recent findings indicate that the translation elongation rate influences mRNA stability. One of the factors that has been implicated in this link between mRNA decay and translation speed is the yeast DEAD-box helicase Dhh1p. Here, we demonstrated that the human ortholog of Dhh1p, DDX6, triggers the deadenylation-dependent decay of inefficiently translated mRNAs in human cells. DDX6 interacts with the ribosome through the Phe-Asp-Phe (FDF) motif in its RecA2 domain. Furthermore, RecA2-mediated interactions and ATPase activity are both required for DDX6 to destabilize inefficiently translated mRNAs. Using ribosome profiling and RNA sequencing, we identified two classes of endogenous mRNAs that are regulated in a DDX6-dependent manner. The identified targets are either translationally regulated or regulated at the steady-state-level and either exhibit signatures of poor overall translation or of locally reduced ribosome translocation rates. Transferring the identified sequence stretches into a reporter mRNA caused translation- and DDX6-dependent degradation of the reporter mRNA. In summary, these results identify DDX6 as a crucial regulator of mRNA translation and decay triggered by slow ribosome movement and provide insights into the mechanism by which DDX6 destabilizes inefficiently translated mRNAs.