59 research outputs found

    Cryo-EM structure of nucleotide-bound Tel1ATM unravels the molecular basis of inhibition and structural rationale for disease-associated mutations

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    Yeast Tel1 and its highly conserved human ortholog ataxia-telangiectasia mutated (ATM) are large protein kinases central to the maintenance of genome integrity. Mutations in ATM are found in ataxia-telangiectasia (A-T) patients and ATM is one of the most frequently mutated genes in many cancers. Using cryoelectron microscopy, we present the structure of Tel1 in a nucleotide-bound state. Our structure reveals molecular details of key residues surrounding the nucleotide binding site and provides a structural and molecular basis for its intrinsically low basal activity. We show that the catalytic residues are in a productive conformation for catalysis, but the phosphatidylinositol 3-kinase-related kinase (PIKK) regulatory domain insert restricts peptide substrate access and the N-lobe is in an open conformation, thus explaining the requirement for Tel1 activation. Structural comparisons with other PIKKs suggest a conserved and common allosteric activation mechanism. Our work also provides a structural rationale for many mutations found in A-T and cancer

    Modeling cancer genomic data in yeast reveals selection against ATM function during tumorigenesis

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    The DNA damage response (DDR) comprises multiple functions that collectively preserve genomic integrity and suppress tumorigenesis. The Mre11 complex and ATM govern a major axis of the DDR and several lines of evidence implicate that axis in tumor suppression. Components of the Mre11 complex are mutated in approximately five percent of human cancers. Inherited mutations of complex members cause severe chromosome instability syndromes, such as Nijmegen Breakage Syndrome, which is associated with strong predisposition to malignancy. And in mice, Mre11 complex mutations are markedly more susceptible to oncogene- induced carcinogenesis. The complex is integral to all modes of DNA double strand break (DSB) repair and is required for the activation of ATM to effect DNA damage signaling. To understand which functions of the Mre11 complex are important for tumor suppression, we undertook mining of cancer genomic data from the clinical sequencing program at Memorial Sloan Kettering Cancer Center, which includes the Mre11 complex among the 468 genes assessed. Twenty five mutations in MRE11 and RAD50 were modeled in S. cerevisiae and in vitro. The mutations were chosen based on recurrence and conservation between human and yeast. We found that a significant fraction of tumor-borne RAD50 and MRE11 mutations exhibited separation of function phenotypes wherein Tel1/ATM activation was severely impaired while DNA repair functions were mildly or not affected. At the molecular level, the gene products of RAD50 mutations exhibited defects in ATP binding and hydrolysis. The data reflect the importance of Rad50 ATPase activity for Tel1/ATM activation and suggest that inactivation of ATM signaling confers an advantage to burgeoning tumor cells

    The First Amendment: Broadening the Information Superhighway

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    Surface Photovoltage Spectroscopy of Cd0.97\text{}_{0.97}Fe0.03\text{}_{0.03}Se and Cd0.97\text{}_{0.97}Fe0.03\text{}_{0.03}Te Crystals

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    The surface electronic structure of the Cd1x\text{}_{1-x}Fex\text{}_{x}Se and Cd1x\text{}_{1-x}Fex\text{}_{x}Τe crystals with x = 0 and x = 0.03 has been studied by Surface Photovoltage Spectroscopy (SPS). The change of surface photovoltage was observed due to photo-excitation of the electrons from the deep donor state Fe 3d to conduction band edge. This gave possibility to determine energy position of the Fe 3d state at 0.64 and 0.15 eV over the top of the valence band for CdSe and CdTe, respectively
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