Article

Impaired DNA Damage Response, Genome Instability, and Tumorigenesis in SIRT1 Mutant Mice

Genetics of Development and Disease Branch, 10/9N105, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Cancer cell (Impact Factor: 23.52). 11/2008; 14(4):312-23. DOI: 10.1016/j.ccr.2008.09.001
Source: PubMed

ABSTRACT

In lower eukaryotes, Sir2 serves as a histone deacetylase and is implicated in chromatin silencing, longevity, and genome stability. Here we mutated the Sirt1 gene, a homolog of yeast Sir2, in mice to study its function. We show that a majority of SIRT1 null embryos die between E9.5 and E14.5, displaying altered histone modification, impaired DNA damage response, and reduced ability to repair DNA damage. We demonstrate that Sirt1(+/-);p53(+/-) mice develop tumors in multiple tissues, whereas activation of SIRT1 by resveratrol treatment reduces tumorigenesis. Finally, we show that many human cancers exhibit reduced levels of SIRT1 compared to normal controls. Thus, SIRT1 may act as a tumor suppressor through its role in DNA damage response and genome integrity.

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    • "SIRT1 has bifurcated roles in tumor progression. It inhibits tumor formation by improving genomic stability [39], but it induces tumor progression by promoting genomic instability, partially by inhibiting p53 through its deacetylation [40]. SIRT6 has common interacting partners with SIRT1, such as c-MYC, HIF1a, and NF-jB [2] [3] [4]. "
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    ABSTRACT: SIRT6, a member of the sirtuin family, has been identified as a candidate tumor suppressor. To pursue the role of SIRT6 in endometrial cancer, we investigated the anti-tumorigenic function of SIRT6. The expression of SIRT6 negatively affected the proliferation of AN3CA and KLE endometrial cancer cells. Increased expression of SIRT6 resulted in the induction of apoptosis by repressing the expression of the anti-apoptotic protein survivin. Consistent with this result, a survivin inhibitor YM155 efficiently inhibited cellular proliferation and induced apoptosis. These results revealed that SIRT6 might function as a tumor suppressor of endometrial cancer cells. Copyright © 2015. Published by Elsevier B.V.
    Full-text · Article · Jul 2015 · FEBS letters
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    • "Previously we reported that embryos homozygous for a null mutation of SIRT1 (Sirt1 -/-) displayed a higher rate of BrdU incorporation at embryonic day 9.5-14.5 (E10.5-14.5) as compared to control embryos at the same stage, yet the underlying mechanism re-mains elusive[28]. To investigate this, murine embryonic fibroblast cells (MEFs) from SIRT1 wild type (WT) and mutant (MT) embryos at passage 1 or 2 were utilized for BrdU labeling analysis. "
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    ABSTRACT: SIRT1, the mammalian homolog of yeast Sir2, is a founding member of a family of 7 protein and histone deacetylases that are involved in numerous biological functions. Previous studies revealed that SIRT1 deficiency results in genome instability, which eventually leads to cancer formation, yet the underlying mechanism is unclear. To investigate this, we conducted a proteomics study and found that SIRT1 interacted with many proteins involved in replication fork protection and origin firing. We demonstrated that loss of SIRT1 resulted in increased replication origin firing, asymmetric fork progression, defective intra-S-phase checkpoint, and chromosome damage. Mechanistically, SIRT1 deacetylates and affects the activity of TopBP1, which plays an essential role in DNA replication fork protection and replication origin firing. Our study demonstrated that ectopic over-expression of the deacetylated form of TopBP1 in SIRT1 mutant cells repressed replication origin firing, while the acetylated form of TopBP1 lost this function. Thus, SIRT1 acts upstream of TopBP1 and plays an essential role in maintaining genome stability by modulating DNA replication fork initiation and the intra-S-phase cell cycle checkpoint.
    Preview · Article · Nov 2014 · International journal of biological sciences
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    • "Classical gene targeting (GT) involves the replacement of an endogenous DNA fragment with an exogenously introduced DNA copy via homologous recombination (HR), which was first reported in yeast 30 years ago (Rothstein 1983). GT in embryonic stem (ES) cells followed by germline chimera formation is a routine in mice and has produced many mouse models available for the study of gene functions and genetic diseases (Capecchi 2005, Wang et al. 2008). A low HR frequency of ~10 −6 and dependence on ES cells have, however , limited this classic GT strategy to mouse (Capecchi 2005) and rat (Tong et al. 2010). "
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    ABSTRACT: Gene replacement (GR) via homologous recombination is a powerful tool for genome editing. Recently, direct GR is achieved successfully by coinjection of mRNAs for engineered endonucleases such as zinc finger nucleases (ZFNs) and donor DNA in developing embryos of diverse organisms. Here, we report the procedures and efficiency for direct GR by using ZFNs in the fish medaka. Upon zygotic coinjection of mRNAs encoding ZFNs that target the gonad-specifically expressed gsdf locus, linear DNA of GR vector pGRgsdf containing the red fluorescent protein (rfp) gene flanked by two homology arms of ~1-kb each underwent GR via homologous recombination. Specifically, 15 of 231 adults from manipulated embryos contained a GR allele in the caudal fin, producing an efficiency of ~7 % for somatic GR. Progeny test revealed that two out of nine fertile fish containing the GR allele in the fin were capable of transmitting the GR allele to ~6 % of F1 generation at adulthood, generating an efficiency of ~22 % for germline transmission. Sequencing and Southern blotting validated precise GR. We show that the GR allele expressed a chimeric gsdf:rfp RNA between gsdf and cointegrated rfp specifically in the gonad, demonstrating recapitulation of endogenous RNA expression as predicted for the defined GR allele. Most importantly, RFP expression coincides faithfully with the gonad-specific gsdf expression in developing embryos and adults. These results demonstrate, for the first time, the feasibility and efficiency of ZFN-mediated precise GR directly in the developing embryo of medaka as a lower vertebrate model.
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