Ataxia Telangiectasia Mutated Proteins

Publication Title: 
The EMBO journal

Telomere loss has been proposed as a mechanism for counting cell divisions during aging in normal somatic cells. How such a mitotic clock initiates the intracellular signalling events that culminate in G1 cell cycle arrest and senescence to restrict the lifespan of normal human cells is not known. We investigated the possibility that critically short telomere length activates a DNA damage response pathway involving p53 and p21(WAF1) in aging cells.

Author(s): 
Vaziri, H.
West, M. D.
Allsopp, R. C.
Davison, T. S.
Wu, Y. S.
Arrowsmith, C. H.
Poirier, G. G.
Benchimol, S.
Publication Title: 
Molecular Biology of the Cell

Forkhead box O (FOXO) transcription factors control diverse cellular functions, such as cell death, metabolism, and longevity. We analyzed FOXO3/FKHRL1 expression and subcellular localization in tumor sections of neuroblastoma patients and observed a correlation between nuclear FOXO3 and high caspase-8 expression. In neuroblastoma caspase-8 is frequently silenced by DNA methylation. Conditional FOXO3 activated caspase-8 gene expression but did not change the DNA-methylation pattern of regulatory sequences in the caspase-8 gene.

Author(s): 
Geiger, Kathrin
Hagenbuchner, Judith
Rupp, Martina
Fiegl, Heidi
Sergi, Consolato
Meister, Bernhard
Kiechl-Kohlendorfer, Ursula
M¸ller, Thomas
Ausserlechner, Michael J.
Obexer, Petra
Publication Title: 
Genes & Development

Alterations in the architecture and dynamics of the nuclear lamina have a causal role in normal and accelerated aging through both cell-autonomous and systemic mechanisms. However, the precise nature of the molecular cues involved in this process remains incompletely defined. Here we report that the accumulation of prelamin A isoforms at the nuclear lamina triggers an ATM- and NEMO-dependent signaling pathway that leads to NF-?B activation and secretion of high levels of proinflammatory cytokines in two different mouse models of accelerated aging (Zmpste24(-/-) and Lmna(G609G/G609G) mice).

Author(s): 
Osorio, Fernando G.
B·rcena, Clea
Soria-Valles, Clara
Ramsay, Andrew J.
de Carlos, FÈlix
Cobo, Juan
Fueyo, Antonio
Freije, JosÈ M. P.
LÛpez-OtÌn, Carlos
Publication Title: 
Genetics

Neurodegeneration is a hallmark of the human disease ataxia-telangiectasia (A-T) that is caused by mutation of the A-T mutated (ATM) gene. We have analyzed Drosophila melanogaster ATM mutants to determine the molecular mechanisms underlying neurodegeneration in A-T. Previously, we found that ATM mutants upregulate the expression of innate immune response (IIR) genes and undergo neurodegeneration in the central nervous system. Here, we present evidence that activation of the IIR is a cause of neurodegeneration in ATM mutants.

Author(s): 
Petersen, Andrew J.
Katzenberger, Rebeccah J.
Wassarman, David A.
Publication Title: 
Blood Cells, Molecules & Diseases

The ability of hematopoietic stem cells (HSCs) to self-renew and differentiate into progenitors is essential for homeostasis of the hematopoietic system. The longevity of HSCs makes them vulnerable to accumulating DNA damage, which may be leukemogenic or result in senescence and cell death. Additionally, the ability of HSCs to self-renew and differentiate allows DNA damage to spread throughout the hematologic system, leaving the organism vulnerable to disease.

Author(s): 
Weiss, Cary N.
Ito, Keisuke
Publication Title: 
Molecular and Cellular Biology

The DNA damage response (DDR) is critical for genome stability and the suppression of a wide variety of human malignancies, including neurodevelopmental disorders, immunodeficiency, and cancer. In addition, the efficacy of many chemotherapeutic strategies is dictated by the status of the DDR. Ubiquitin-specific protease 28 (USP28) was reported to govern the stability of multiple factors that are critical for diverse aspects of the DDR. Here, we examined the effects of USP28 depletion on the DDR in cells and in vivo.

Author(s): 
Knobel, Philip A.
Belotserkovskaya, Rimma
Galanty, Yaron
Schmidt, Christine K.
Jackson, Stephen P.
Stracker, Travis H.
Publication Title: 
Cancer Research

Telomeres are elongated by the enzyme telomerase, which contains a template-bearing RNA (TER or TERC) and a protein reverse transcriptase. Overexpression of a particular mutant human TER with a mutated template sequence (MT-hTer-47A) in telomerase-positive cancer cells causes incorporation of mutant telomeric sequences, telomere uncapping, and initiation of a DNA damage response, ultimately resulting in cell growth inhibition and apoptosis. The DNA damage pathways underlying these cellular effects are not well understood.

Author(s): 
Stohr, Bradley A.
Blackburn, Elizabeth H.
Publication Title: 
Current biology: CB

BACKGROUND: Telomerase is a ribonucleoprotein that copies a short RNA template into telomeric DNA, maintaining eukaryotic chromosome ends and preventing replicative senescence. Telomeres differentiate chromosome ends from DNA double-stranded breaks. Nevertheless, the DNA damage-responsive ATM kinases Tel1p and Mec1p are required for normal telomere maintenance in Saccharomyces cerevisiae. We tested whether the ATM kinases are required for telomerase enzyme activity or whether it is their action on the telomere that allows telomeric DNA synthesis.

Author(s): 
Chan, S. W.
Chang, J.
Prescott, J.
Blackburn, E. H.
Publication Title: 
Molecular Cell

Mammalian telomeres consist of tandem DNA repeats that bind protective protein factors collectively termed shelterins. Telomere disruption typically results in genome instability induced by telomere fusions. The mechanism of telomere fusion varies depending on the means of telomere disruption. Here, we investigate telomere fusions caused by overexpression of mutant telomerases that add mutated telomeric repeats, thereby compromising shelterin binding to telomeric termini.

Author(s): 
Stohr, Bradley A.
Xu, Lifeng
Blackburn, Elizabeth H.
Publication Title: 
Molecular Cell

Using a modified single telomere length analysis protocol (STELA) to clone and examine the sequence composition of individual human XpYp telomeres, we discovered a distinct class of extremely short telomeres in human cancer cells with active telomerase. We name them "t-stumps," to distinguish them from the well-regulated longer bulk telomeres. T-stumps contained arrangements of telomeric repeat variants and a minimal run of seven canonical telomeric TTAGGG repeats, but all could bind at least one TRF1 or TRF2 in vitro.

Author(s): 
Xu, Lifeng
Blackburn, Elizabeth H.

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