title: STN1 protects chromosome ends in Arabidopsis thaliana.
abstract: Telomeres shield the natural ends of chromosomes from nucleolytic attack, recognition as double-strand breaks, and inappropriate processing by DNA repair machinery. The trimeric Stn1/Ten1/Cdc13 complex is critical for chromosome end protection in Saccharomyces cerevisiae, while vertebrate telomeres are protected by shelterin, a complex of six proteins that does not include STN1 or TEN1. Recent studies demonstrate that Stn1 and Ten1 orthologs in Schizosaccharomyces pombe contribute to telomere integrity in a complex that is distinct from the shelterin components, Pot1 and Tpp1. Thus, chromosome-end protection may be mediated by distinct subcomplexes of telomere proteins. Here we report the identification of a STN1 gene in Arabidopsis that is essential for chromosome-end protection. AtSTN1 encodes an 18-kDa protein bearing a single oligonucleotide/oligosaccharide binding fold with significant sequence similarity to the yeast Stn1 proteins. Plants null for AtSTN1 display an immediate onset of growth and developmental defects and reduced fertility. These outward phenotypes are accompanied by catastrophic loss of telomeric and subtelomeric DNA, high levels of end-to-end chromosome fusions, increased G-overhang signals, and elevated telomere recombination. Thus, AtSTN1 is a crucial component of the protective telomere cap in Arabidopsis, and likely in other multicellular eukaryotes.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843-2128, USA.
authors.forename: Xiangyu
authors.initials: X
authors.lastname: Song
authors.forename: Katherine
authors.initials: K
authors.lastname: Leehy
authors.forename: Ross T
authors.initials: RT
authors.lastname: Warrington
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Lamb
authors.forename: Yulia V
authors.initials: YV
authors.lastname: Surovtseva
authors.forename: Dorothy E
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism*; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D016615:Telomere / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D029681:Arabidopsis Proteins; D002868:Chromosomal Proteins, Non-Histone; C534225:STN1 protein, Arabidopsis