title: Dyskerin is a component of the Arabidopsis telomerase RNP required for telomere maintenance.
abstract: Dyskerin binds the H/ACA box of human telomerase RNA and is a core telomerase subunit required for RNP biogenesis and enzyme function in vivo. Missense mutations in dyskerin result in dyskeratosis congenita, a complex syndrome characterized by bone marrow failure, telomerase enzyme deficiency, and progressive telomere shortening. Here we demonstrate that dyskerin also contributes to telomere maintenance in Arabidopsis thaliana. We report that both AtNAP57, the Arabidopsis dyskerin homolog, and AtTERT, the telomerase catalytic subunit, accumulate in the plant nucleolus, and AtNAP57 associates with active telomerase RNP particles in an RNA-dependent manner. Furthermore, AtNAP57 interacts in vitro with AtPOT1a, a novel component of Arabidopsis telomerase. Although a null mutation in AtNAP57 is lethal, AtNAP57, like AtTERT, is not haploinsufficient for telomere maintenance in Arabidopsis. However, introduction of an AtNAP57 allele containing a T66A mutation decreased telomerase activity in vitro, disrupted telomere length regulation on individual chromosome ends in vivo, and established a new, shorter telomere length set point. These results imply that T66A NAP57 behaves as a dominant-negative inhibitor of telomerase. We conclude that dyskerin is a conserved component of the telomerase RNP complex in higher eukaryotes that is required for maximal enzyme activity in vivo.
authors.affiliation: Texas A&M University, Department of Biochemistry and Biophysics, 2128 TAMU, College Station, Texas 77843-2128, USA.
authors.forename: Kalpana
authors.initials: K
authors.lastname: Kannan
authors.forename: Andrew D L
authors.initials: AD
authors.lastname: Nelson
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002478:Cells, Cultured / Q000378:metabolism / Q000648:ultrastructure; D032461:Chromosomes, Plant / Q000378:metabolism / Q000648:ultrastructure*; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D006801:Humans; D006836:Hydro-Lyases / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017354:Point Mutation; D025941:Protein Interaction Mapping; D012323:RNA Processing, Post-Transcriptional; D018749:RNA, Plant / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D000089804:Shelterin Complex; D019098:Telomerase / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism / Q000648:ultrastructure*; D034501:Telomere-Binding Proteins / Q000378:metabolism*; D014529:Uridine / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D004268:DNA-Binding Proteins; C463462:KU70 protein, Arabidopsis; C462839:NAP57 protein, Arabidopsis; D009687:Nuclear Proteins; C528256:POT1A protein, Arabidopsis; C503876:Pot1 protein, Arabidopsis; D018749:RNA, Plant; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; C528255:TERT protein, Arabidopsis; D019098:Telomerase; D006836:Hydro-Lyases; C022479:pseudouridylate synthetase; D014529:Uridine