title: Apollo, an Artemis-related nuclease, interacts with TRF2 and protects human telomeres in S phase.
abstract: Human chromosome ends are protected by shelterin, an abundant six-subunit protein complex that binds specifically to the telomeric-repeat sequences, regulates telomere length, and ensures that chromosome ends do not elicit a DNA-damage response (reviewed in). Using mass spectrometry of proteins associated with the shelterin component Rap1, we identified an SMN1/PSO2 nuclease family member that is closely related to Artemis. We refer to this protein as Apollo and report that Apollo has the ability to localize to telomeres through an interaction with the shelterin component TRF2. Although its low abundance at telomeres indicates that Apollo is not a core component of shelterin, Apollo knockdown with RNAi resulted in senescence and the activation of a DNA-damage signal at telomeres as evidenced by telomere-dysfunction-induced foci (TIFs). The TIFs occurred primarily in S phase, suggesting that Apollo contributes to a processing step associated with the replication of chromosome ends. Furthermore, some of the metaphase chromosomes showed two telomeric signals at single-chromatid ends, suggesting an aberrant telomere structure. We propose that the Artemis-like nuclease Apollo is a shelterin accessory factor required for the protection of telomeres during or after their replication.
authors.affiliation: Laboratory for Cell Biology and Genetics, The Rockefeller University, 1230 York Avenue, New York, New York 10021, USA.
authors.forename: Megan
authors.initials: M
authors.lastname: van Overbeek
authors.forename: Titia
authors.initials: T
authors.lastname: de Lange
mesh_terms: D002460:Cell Line; D002877:Chromosomes, Human / Q000378:metabolism / Q000648:ultrastructure; D004249:DNA Damage; D045643:DNA Repair Enzymes; D003851:Deoxyribonucleases / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D009687:Nuclear Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D016196:S Phase / Q000502:physiology*; D000089804:Shelterin Complex; D016615:Telomere / Q000378:metabolism* / Q000648:ultrastructure; D034501:Telomere-Binding Proteins / Q000378:metabolism; D035341:Telomeric Repeat Binding Protein 2 / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D035341:Telomeric Repeat Binding Protein 2; C493741:DCLRE1B protein, human; D003851:Deoxyribonucleases; D005090:Exodeoxyribonucleases; D045643:DNA Repair Enzymes