title: Essential roles of Xenopus TRF2 in telomere end protection and replication.
abstract: TRF1 and TRF2 are double-stranded (ds) telomere DNA-binding proteins and the core members of shelterin, a complex that provides the structural and functional basis of telomere functions. We have reported that unlike mammalian TRF1 that constitutively binds to chromatin, Xenopus TRF1 (xTRF1) associates with mitotic chromatin but dissociates from interphase chromatin reconstituted in Xenopus egg extracts. This finding raised the possibility that xTRF1 and Xenopus TRF2 (xTRF2) contribute to telomere functions in a manner different from mammalian TRF1 and TRF2. Here, we focused on the role of xTRF2. We prepared chromatin reconstituted in egg extracts immunodepleted for xTRF2. Compared to mock-depleted nuclei, DNA damage response at telomeres was activated, and bulk DNAs were poorly replicated in xTRF2-depleted nuclei. The replication defect was rescued by inactivating ATR through the addition of anti-ATR neutralizing antibody, suggesting that ATR plays a role in the defect. Interestingly, the bulk DNA replication defect, but not the DNA damage response at telomeres, was rescued by supplementing the xTRF2-depleted extracts with recombinant xTRF2 (rTRF2). We propose that xTRF2 is required for both efficient replication of bulk DNA and protection from the activation of the DNA damage checkpoints pathway, and that those two functions are mechanistically separable.
authors.affiliation: Laboratory of Cell Cycle Regulation, Department of Gene Mechanisms, Graduate School of Biostudies, Kyoto University, Yoshida-Konoe-cho, Sakyo-ku, Kyoto 606-8501, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Muraki
authors.forename: Akira
authors.initials: A
authors.lastname: Nabetani
authors.forename: Atsuya
authors.initials: A
authors.lastname: Nishiyama
authors.forename: Fuyuki
authors.initials: F
authors.lastname: Ishikawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004261:DNA Replication / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D023061:Gene Order; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D016415:Sequence Alignment; D016615:Telomere / Q000235:genetics* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000378:metabolism; D035341:Telomeric Repeat Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D014981:Xenopus / Q000235:genetics* / Q000378:metabolism*; D029867:Xenopus Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D034501:Telomere-Binding Proteins; D035341:Telomeric Repeat Binding Protein 2; D025521:Tumor Suppressor Proteins; D029867:Xenopus Proteins; C576898:Atr protein, Xenopus; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases