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The ATM repair pathway inhibits RNA polymerase I transcription in response to chromosome breaks

Experimental Immunology, NCI.
Nature (Impact Factor: 42.35). 07/2007; 447(7145):730-4. DOI: 10.1038/nature05842
Source: PubMed

ABSTRACT DNA lesions interfere with DNA and RNA polymerase activity. Cyclobutane pyrimidine dimers and photoproducts generated by ultraviolet irradiation cause stalling of RNA polymerase II, activation of transcription-coupled repair enzymes, and inhibition of RNA synthesis. During the S phase of the cell cycle, collision of replication forks with damaged DNA blocks ongoing DNA replication while also triggering a biochemical signal that suppresses the firing of distant origins of replication. Whether the transcription machinery is affected by the presence of DNA double-strand breaks remains a long-standing question. Here we monitor RNA polymerase I (Pol I) activity in mouse cells exposed to genotoxic stress and show that induction of DNA breaks leads to a transient repression in Pol I transcription. Surprisingly, we find Pol I inhibition is not itself the direct result of DNA damage but is mediated by ATM kinase activity and the repair factor proteins NBS1 (also known as NLRP2) and MDC1. Using live-cell imaging, laser micro-irradiation, and photobleaching technology we demonstrate that DNA lesions interfere with Pol I initiation complex assembly and lead to a premature displacement of elongating holoenzymes from ribosomal DNA. Our data reveal a novel ATM/NBS1/MDC1-dependent pathway that shuts down ribosomal gene transcription in response to chromosome breaks.

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Available from: Michael J Kruhlak, May 20, 2015
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    • "By combining these results with our recent work on the genomic architecture of NORs, we can now present a model for how integrity of rDNA arrays is maintained against an onslaught of DNA damage (Fig. 7). While the use of γ-irradiation and laser microirradiation to induce DSBs has yielded conflicting results (Kruhlak et al. 2007; Moore et al. 2011; Larsen et al. 2014), here we unequivocally demonstrated that DSBs within rDNA are sufficient to induce ATM-dependent inhibition of Pol I transcription. The introduction of the CRISPR/Cas9 allowed us to demonstrate that DSBs in both transcribed and nontranscribed regions of the rDNA repeat induce this response. "
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    ABSTRACT: DNA double-strand breaks (DSBs) are repaired by two main pathways: nonhomologous end-joining and homologous recombination (HR). Repair pathway choice is thought to be determined by cell cycle timing and chromatin context. Nucleoli, prominent nuclear subdomains and sites of ribosome biogenesis, form around nucleolar organizer regions (NORs) that contain rDNA arrays located on human acrocentric chromosome p-arms. Actively transcribed rDNA repeats are positioned within the interior of the nucleolus, whereas sequences proximal and distal to NORs are packaged as heterochromatin located at the nucleolar periphery. NORs provide an opportunity to investigate the DSB response at highly transcribed, repetitive, and essential loci. Targeted introduction of DSBs into rDNA, but not abutting sequences, results in ATM-dependent inhibition of their transcription by RNA polymerase I. This is coupled with movement of rDNA from the nucleolar interior to anchoring points at the periphery. Reorganization renders rDNA accessible to repair factors normally excluded from nucleoli. Importantly, DSBs within rDNA recruit the HR machinery throughout the cell cycle. Additionally, unscheduled DNA synthesis, consistent with HR at damaged NORs, can be observed in G1 cells. These results suggest that HR can be templated in cis and suggest a role for chromosomal context in the maintenance of NOR genomic stability. © 2015 van Sluis and McStay; Published by Cold Spring Harbor Laboratory Press.
    Genes & Development 06/2015; 29(11). DOI:10.1101/gad.260703.115 · 12.64 Impact Factor
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    • "Interestingly, Treacle, like MDC1, contains several phoshorylated SDT domains that mediate NBS1 binding, suggesting a conserved mechanism of NBS1 retention in the nucleus and nucleolus. It is notable that while MDC1 is not required for NBS1 retention to nucleoli, MDC1 deficient cells failed to silence rDNA transcription after IR treatment [57]. This may reflect a difference between the techniques used, as IR could induce damage directly in nucleolar DNA, or could indicate that MRE11 complex localization per se is not sufficient for rDNA silencing. "
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    ABSTRACT: Newly identified interactions with the FHA and BRCT domains of NBS1 influence subcellular localization of the MRE11 complex.•The MRE11 complex promotes TOPBP1 recruitment and ATR activation during replication stress.•The MRE11 complex is a barrier to oncogene-induced tumorigenesis.
    Experimental Cell Research 10/2014; 329(1). DOI:10.1016/j.yexcr.2014.10.010 · 3.37 Impact Factor
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    • "This type of histone modification spreads over about 2 Mb surrounding a break [75] [76]. Additionally, chromatin relaxation in the area surrounding DNA damage [77] potentiates the ATM signaling and radioresistance [78], as demonstrated by using histone deacetylase inhibitors and chromatin-modifying agents, such as chloroquine or osmotic shock [46]. Moreover, it has been suggested that, by regulation of the level of acetylation of Lys 14 of histone H3 (H3 K14) before and after DSBs, the nucleosome-binding protein HMGN1 optimizes activation of ATM [79]. "
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    ABSTRACT: The mammalian protein kinase ataxia telangiectasia mutated (ATM) is a key regulator of the DNA double-strand-break response and belongs to the evolutionary conserved phosphatidylinositol-3-kinase-related protein kinases. ATM deficiency causes ataxia telangiectasia (AT), a genetic disorder that is characterized by premature aging, cerebellar neuropathy, immunodeficiency, and predisposition to cancer. AT cells show defects in theDNA damage-response pathway, cell-cycle control, and telomere maintenance and length regulation. Likewise, in Saccharomyces cerevisiae, haploid strains defective in the TEL1 gene, the ATM ortholog, show chromosomal aberrations and short telomeres. In this review, we outline the complex role of ATM/Tel1 in maintaining genomic stability through its control of numerous aspects of cellular survival. In particular, we describe how ATM/Tel1 participates in the signal transduction pathways elicited by DNA damage and in telomere homeostasis and its importance as a barrier to cancer development.
    BioMed Research International 08/2014; Volume 2014(Article ID 787404):17 pages. DOI:10.1155/2014/787404 · 2.71 Impact Factor
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