SMC5/6 is required for replication fork stability and faithful chromosome segregation during neurogenesis

  1. Alisa Atkins
  2. Michelle J Xu
  3. Maggie Li
  4. Nathaniel P Rogers
  5. Marina V Pryzhkova  Is a corresponding author
  6. Philip W Jordan  Is a corresponding author
  1. Johns Hopkins Bloomberg School of Public Health, United States

Abstract

Mutations of SMC5/6 components cause developmental defects, including primary microcephaly. To model neurodevelopmental defects, we engineered a mouse wherein Smc5 is conditionally knocked out (cKO) in the developing neocortex. Smc5 cKO mice exhibited neurodevelopmental defects due to neural progenitor cell (NPC) apoptosis, which led to reduction in cortical layer neurons. Smc5 cKO NPCs formed DNA bridges during mitosis and underwent chromosome missegregation. SMC5/6 depletion triggers a CHEK2-p53 DNA damage response, as concomitant deletion of the Trp53 tumor suppressor or Chek2 DNA damage checkpoint kinase rescued Smc5 cKO neurodevelopmental defects. Further assessment using Smc5 cKO and auxin-inducible degron systems demonstrated that absence of SMC5/6 leads to DNA replication stress at late-replicating regions such as pericentromeric heterochromatin regions. In summary, SMC5/6 is important for completion of DNA replication prior to entering mitosis, which ensures accurate chromosome segregation. Thus, SMC5/6 functions are critical in highly proliferative stem cells during organism development.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files.

Article and author information

Author details

  1. Alisa Atkins

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Michelle J Xu

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Maggie Li

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-1047-1554
  4. Nathaniel P Rogers

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, New Orleans, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-0411-5249
  5. Marina V Pryzhkova

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
    For correspondence
    mpryzhk1@jhu.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-3462-5768
  6. Philip W Jordan

    Biochemistry and Molecular Biology, Johns Hopkins Bloomberg School of Public Health, Baltimore, United States
    For correspondence
    pjordan8@jhu.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-4890-2647

Funding

National Institute of General Medical Sciences (R01GM11755)

  • Philip W Jordan

National Institutes of Health (R21OD023720)

  • Philip W Jordan

National Institute of Neurological Disorders and Stroke (R03NS106486)

  • Philip W Jordan

Johns Hopkins University (Catalyst Award)

  • Philip W Jordan

National Cancer Institute (T32CA009110)

  • Michelle J Xu

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Kevin Struhl, Harvard Medical School, United States

Ethics

Animal experimentation: All mice were bred at Johns Hopkins University (JHU, Baltimore, MD) in accordance with the National Institutes of Health and U.S. Department of Agriculture criteria and protocols for their care and use were approved by the Institutional Animal Care and Use Committees (IACUC) of JHU (Protocol number = MO19H08).

Version history

  1. Received: July 16, 2020
  2. Accepted: November 16, 2020
  3. Accepted Manuscript published: November 17, 2020 (version 1)
  4. Version of Record published: December 8, 2020 (version 2)

Copyright

© 2020, Atkins 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.

Metrics

  • 3,545
    views
  • 363
    downloads
  • 20
    citations

Views, downloads and citations are aggregated across all versions of this paper published by eLife.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Alisa Atkins
  2. Michelle J Xu
  3. Maggie Li
  4. Nathaniel P Rogers
  5. Marina V Pryzhkova
  6. Philip W Jordan
(2020)
SMC5/6 is required for replication fork stability and faithful chromosome segregation during neurogenesis
eLife 9:e61171.
https://doi.org/10.7554/eLife.61171

Share this article

https://doi.org/10.7554/eLife.61171

Further reading

    1. Biochemistry and Chemical Biology
    2. Chromosomes and Gene Expression
    Ramona Weber, Chung-Te Chang
    Research Article

    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.

    1. Chromosomes and Gene Expression
    Marwan Anoud, Emmanuelle Delagoutte ... Jean-Paul Concordet
    Research Article

    Tardigrades are microscopic animals renowned for their ability to withstand extreme conditions, including high doses of ionizing radiation (IR). To better understand their radio-resistance, we first characterized induction and repair of DNA double- and single-strand breaks after exposure to IR in the model species Hypsibius exemplaris. Importantly, we found that the rate of single-strand breaks induced was roughly equivalent to that in human cells, suggesting that DNA repair plays a predominant role in tardigrades’ radio-resistance. To identify novel tardigrade-specific genes involved, we next conducted a comparative transcriptomics analysis across three different species. In all three species, many DNA repair genes were among the most strongly overexpressed genes alongside a novel tardigrade-specific gene, which we named Tardigrade DNA damage Response 1 (TDR1). We found that TDR1 protein interacts with DNA and forms aggregates at high concentration suggesting it may condensate DNA and preserve chromosome organization until DNA repair is accomplished. Remarkably, when expressed in human cells, TDR1 improved resistance to Bleomycin, a radiomimetic drug. Based on these findings, we propose that TDR1 is a novel tardigrade-specific gene conferring resistance to IR. Our study sheds light on mechanisms of DNA repair helping cope with high levels of DNA damage inflicted by IR.