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Blood. 2017 May 4;129(18):2479-2492. doi: 10.1182/blood-2016-06-725093. Epub 2017 Mar 7.

Ssb1 and Ssb2 cooperate to regulate mouse hematopoietic stem and progenitor cells by resolving replicative stress.

Author information

1
QIMR Berghofer Medical Research Institute, Herston, QLD, Australia.
2
School of Medicine, University of Queensland, Brisbane, QLD, Australia.
3
Laboratory of Bioinformatics and Systems Biology, Center of New Technologies, University of Warsaw, Warsaw, Poland.
4
Department of Biochemistry & Molecular Biology, Institute for Translational Sciences, University of Texas Medical Branch, Galveston, TX.
5
Department of Radiation Oncology, The Houston Methodist Research Institute, Houston, TX.
6
School of Natural Sciences, Griffith University, Nathan, Brisbane, QLD, Australia.
7
Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm, Sweden.
8
Centre for Clinical Research, Cancer and Neuroscience, University of Queensland, Brisbane, QLD, Australia.
9
South Australia Pathology and School of Veterinary Science, University of Adelaide, Adelaide, SA, Australia.
10
Department of Pathology, Cancer Institute, New York University School of Medicine, New York, NY.
11
St. Vincent's Institute of Medical Research and Department of Medicine, St. Vincent's Hospital, University of Melbourne, Fitzroy, VIC, Australia; and.
12
Department of Haematology, Royal Brisbane and Women's Hospital, Brisbane, QLD, Australia.

Abstract

Hematopoietic stem and progenitor cells (HSPCs) are vulnerable to endogenous damage and defects in DNA repair can limit their function. The 2 single-stranded DNA (ssDNA) binding proteins SSB1 and SSB2 are crucial regulators of the DNA damage response; however, their overlapping roles during normal physiology are incompletely understood. We generated mice in which both Ssb1 and Ssb2 were constitutively or conditionally deleted. Constitutive Ssb1/Ssb2 double knockout (DKO) caused early embryonic lethality, whereas conditional Ssb1/Ssb2 double knockout (cDKO) in adult mice resulted in acute lethality due to bone marrow failure and intestinal atrophy featuring stem and progenitor cell depletion, a phenotype unexpected from the previously reported single knockout models of Ssb1 or Ssb2 Mechanistically, cDKO HSPCs showed altered replication fork dynamics, massive accumulation of DNA damage, genome-wide double-strand breaks enriched at Ssb-binding regions and CpG islands, together with the accumulation of R-loops and cytosolic ssDNA. Transcriptional profiling of cDKO HSPCs revealed the activation of p53 and interferon (IFN) pathways, which enforced cell cycling in quiescent HSPCs, resulting in their apoptotic death. The rapid cell death phenotype was reproducible in in vitro cultured cDKO-hematopoietic stem cells, which were significantly rescued by nucleotide supplementation or after depletion of p53. Collectively, Ssb1 and Ssb2 control crucial aspects of HSPC function, including proliferation and survival in vivo by resolving replicative stress to maintain genomic stability.

PMID:
28270450
PMCID:
PMC5418634
DOI:
10.1182/blood-2016-06-725093
[Indexed for MEDLINE]
Free PMC Article

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