title: Identification of candidate alternative lengthening of telomeres genes by methionine restriction and RNA interference.
abstract: Telomerase-negative cancer cells can maintain their telomeres by a recombination-mediated alternative lengthening of telomeres (ALT) process. We reported previously that sequestration of MRE11/RAD50/NBS1 complexes represses ALT-mediated telomere length maintenance, and suppresses formation of ALT-associated promyelocytic leukemia (PML) bodies (APBs). APBs are PML bodies containing telomeric DNA and telomere-binding proteins, and are observed only in a small fraction of cells within asynchronously dividing ALT-positive cell populations. Here, we report that methionine restriction caused a reversible arrest in G0/G1 phase of the cell cycle and reversible induction of APB formation in most cells within an ALT-positive population. We combined methionine restriction with RNA interference to test whether the following proteins are required for APB formation: PML body-associated proteins, PML and Sp100; telomere-associated proteins, TRF1, TRF2, TIN2 and RAP1; and DNA repair proteins, MRE11, RAD50, NBS1 and 53BP1. APB formation was not decreased by depletion of Sp100 (as reported previously) or of 53BP1, although 53BP1 partially colocalizes with APBs. Depletion of the other proteins suppressed APB formation. Because of the close linkage between ALT-mediated telomere maintenance and ability to form APBs, the eight proteins identified by this screen as being required for APB formation are also likely to be required for the ALT mechanism.
authors.affiliation: Cancer Research Unit, Children's Medical Research Institute, Westmead, NSW, Australia.
authors.forename: W-Q
authors.initials: WQ
authors.lastname: Jiang
authors.forename: Z-H
authors.initials: ZH
authors.lastname: Zhong
authors.forename: J D
authors.initials: JD
authors.lastname: Henson
authors.forename: R R
authors.initials: RR
authors.lastname: Reddel
mesh_terms: D017766:Acid Anhydride Hydrolases; D034961:Antigens, Nuclear / Q000235:genetics / Q000502:physiology; D001324:Autoantigens / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D045643:DNA Repair Enzymes / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D016193:G1 Phase; D005821:Genetic Techniques; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000076228:MRE11 Homologue Protein; D008715:Methionine / Q000172:deficiency; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D009687:Nuclear Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000071156:Promyelocytic Leukemia Protein; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D016192:Resting Phase, Cell Cycle; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D035321:Telomeric Repeat Binding Protein 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D035341:Telomeric Repeat Binding Protein 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology; D000071857:Tumor Suppressor p53-Binding Protein 1
chemical_list: D034961:Antigens, Nuclear; D001324:Autoantigens; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D034741:RNA, Small Interfering; C440868:TINF2 protein, human; C498301:TP53BP1 protein, human; D034501:Telomere-Binding Proteins; D035321:Telomeric Repeat Binding Protein 1; D035341:Telomeric Repeat Binding Protein 2; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D000071857:Tumor Suppressor p53-Binding Protein 1; C066642:SP100 protein, human; C070576:PML protein, human; D008715:Methionine; D000076228:MRE11 Homologue Protein; D017766:Acid Anhydride Hydrolases; C112158:RAD50 protein, human; D045643:DNA Repair Enzymes