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  • 1
    Publication Date: 2009-05-05
    Description: In response to DNA damage, eukaryotic cells initiate a complex signalling pathway, termed the DNA damage response (DDR), which coordinates cell cycle arrest with DNA repair. Studies have shown that oncogene-induced senescence, which provides a barrier to tumour development, involves activation of the DDR. Using a genome-wide RNA interference (RNAi) screen, we have identified 17 factors required for oncogenic BRAF to induce senescence in primary fibroblasts and melanocytes. One of these factors is an F-box protein, FBXO31, a candidate tumour suppressor encoded in 16q24.3, a region in which there is loss of heterozygosity in breast, ovarian, hepatocellular and prostate cancers. Here we study the cellular role of FBXO31, identify its target substrate and determine the basis for its growth inhibitory activity. We show that ectopic expression of FBXO31 acts through a proteasome-directed pathway to mediate the degradation of cyclin D1, an important regulator of progression from G1 to S phase, resulting in arrest in G1. Cyclin D1 degradation results from a direct interaction with FBXO31 and is dependent on the F-box motif of FBXO31 and phosphorylation of cyclin D1 at Thr 286, which is known to be required for cyclin D1 proteolysis. The involvement of the DDR in oncogene-induced senescence prompted us to investigate the role of FBXO31 in DNA repair. We find that DNA damage induced by gamma-irradiation results in increased FBXO31 levels, which requires phosphorylation of FBXO31 by the DDR-initiating kinase ATM. RNAi-mediated knockdown of FBXO31 prevents cells from undergoing efficient arrest in G1 after gamma-irradiation and markedly increases sensitivity to DNA damage. Finally, we show that a variety of DNA damaging agents all result in a large increase in FBXO31 levels, indicating that induction of FBXO31 is a general response to genotoxic stress. Our results reveal FBXO31 as a regulator of the G1/S transition that is specifically required for DNA damage-induced growth arrest.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722223/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2722223/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Santra, Manas K -- Wajapeyee, Narendra -- Green, Michael R -- Howard Hughes Medical Institute/ -- England -- Nature. 2009 Jun 4;459(7247):722-5. doi: 10.1038/nature08011. Epub 2009 May 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Howard Hughes Medical Institute, Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19412162" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylcysteine/analogs & derivatives/pharmacology ; Ataxia Telangiectasia Mutated Proteins ; Cell Cycle Proteins/metabolism ; Cell Line, Tumor ; Cyclin D1/*metabolism ; Cysteine Proteinase Inhibitors/pharmacology ; DNA Damage/drug effects/*genetics ; DNA-Binding Proteins/metabolism ; F-Box Proteins/*metabolism ; G1 Phase/*physiology ; Humans ; Melanoma/genetics/physiopathology ; Proteasome Endopeptidase Complex/metabolism ; Protein-Serine-Threonine Kinases/metabolism ; Transcriptional Activation ; Tumor Suppressor Proteins/*metabolism ; Ubiquitination
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2014-12-04
    Description: The TRIM37 (also known as MUL) gene is located in the 17q23 chromosomal region, which is amplified in up to approximately 40% of breast cancers. TRIM37 contains a RING finger domain, a hallmark of E3 ubiquitin ligases, but its protein substrate(s) is unknown. Here we report that TRIM37 mono-ubiquitinates histone H2A, a chromatin modification associated with transcriptional repression. We find that in human breast cancer cell lines containing amplified 17q23, TRIM37 is upregulated and, reciprocally, the major H2A ubiquitin ligase RNF2 (also known as RING1B) is downregulated. Genome-wide chromatin immunoprecipitation (ChIP)-chip experiments in 17q23-amplified breast cancer cells identified many genes, including multiple tumour suppressors, whose promoters were bound by TRIM37 and enriched for ubiquitinated H2A. However, unlike RNF2, which is a subunit of polycomb repressive complex 1 (PRC1), we find that TRIM37 associates with polycomb repressive complex 2 (PRC2). TRIM37, PRC2 and PRC1 are co-bound to specific target genes, resulting in their transcriptional silencing. RNA-interference-mediated knockdown of TRIM37 results in loss of ubiquitinated H2A, dissociation of PRC1 and PRC2 from target promoters, and transcriptional reactivation of silenced genes. Knockdown of TRIM37 in human breast cancer cells containing amplified 17q23 substantially decreases tumour growth in mouse xenografts. Conversely, ectopic expression of TRIM37 renders non-transformed cells tumorigenic. Collectively, our results reveal TRIM37 as an oncogenic H2A ubiquitin ligase that is overexpressed in a subset of breast cancers and promotes transformation by facilitating silencing of tumour suppressors and other genes.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4269325/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4269325/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bhatnagar, Sanchita -- Gazin, Claude -- Chamberlain, Lynn -- Ou, Jianhong -- Zhu, Xiaochun -- Tushir, Jogender S -- Virbasius, Ching-Man -- Lin, Ling -- Zhu, Lihua J -- Wajapeyee, Narendra -- Green, Michael R -- R01 GM033977/GM/NIGMS NIH HHS/ -- R01GM033977/GM/NIGMS NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2014 Dec 4;516(7529):116-20. doi: 10.1038/nature13955. Epub 2014 Nov 24.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Howard Hughes Medical Institute, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA [2] Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. ; CEA/DSV/iRCM/LEFG, Genopole G2, and Universite Paris Diderot, 91057 Evry, France. ; Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. ; Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, Connecticut 06877, USA. ; 1] Programs in Gene Function and Expression and Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA [2] Program in Bioinformatics and Integrative Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA. ; Department of Pathology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25470042" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Breast Neoplasms/*enzymology/*genetics ; Female ; Gene Expression Profiling ; *Gene Expression Regulation, Neoplastic ; Gene Knockdown Techniques ; Gene Silencing ; Heterografts ; Histones/metabolism ; Humans ; MCF-7 Cells ; Mice ; NIH 3T3 Cells ; Nuclear Proteins/*genetics/*metabolism ; Oncogene Proteins/*genetics/metabolism ; Polycomb Repressive Complex 1/*genetics/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2014-08-18
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
  • 5
    Publication Date: 2014-09-03
    Description: X-chromosome inactivation (XCI), the random transcriptional silencing of one X chromosome in somatic cells of female mammals, is a mechanism that ensures equal expression of X-linked genes in both sexes. XCI is initiated in cis by the noncoding Xist RNA, which coats the inactive X chromosome (Xi) from which it...
    Keywords: Inaugural Articles
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 6
    Publication Date: 2015-01-10
    Description: Serine/threonine kinase 11 (STK11, also known as LKB1) functions as a tumor suppressor in many human cancers. However, paradoxically loss of LKB1 in mouse embryonic fibroblast results in resistance to oncogene-induced transformation. Therefore, it is unclear why loss of LKB1 leads to increased predisposition to develop a wide variety of cancers. Here, we show that LKB1 protects cells from genotoxic stress. Cells lacking LKB1 display increased sensitivity to irradiation, accumulates more DNA double-strand breaks, display defective homology-directed DNA repair (HDR) and exhibit increased mutation rate, compared with that of LKB1-expressing cells. Conversely, the ectopic expression of LKB1 in cells lacking LKB1 protects them against genotoxic stress-induced DNA damage and prevents the accumulation of mutations. We find that LKB1 post-transcriptionally stimulates HDR gene BRCA1 expression by inhibiting the cytoplasmic localization of the RNA-binding protein, HU antigen R, in an AMP kinase-dependent manner and stabilizes BRCA1 mRNA. Cells lacking BRCA1 similar to the cell lacking LKB1 display increased genomic instability and ectopic expression of BRCA1 rescues LKB1 loss-induced sensitivity to genotoxic stress. Collectively, our results demonstrate that LKB1 is a crucial regulator of genome integrity and reveal a novel mechanism for LKB1-mediated tumor suppression with direct therapeutic implications for cancer prevention.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 7
    Publication Date: 2014-07-30
    Description: Tumor suppressor p53 plays an important role in mediating growth inhibition upon telomere dysfunction. Here, we show that loss of the p53 target gene cyclin-dependent kinase inhibitor 1A (CDKN1A, also known as p21WAF1/CIP1) increases apoptosis induction following telomerase inhibition in a variety of cancer cell lines and mouse xenografts. This...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 8
    Publication Date: 2003-11-01
    Print ISSN: 0006-3134
    Electronic ISSN: 1573-8264
    Topics: Biology
    Published by Springer
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