title: Evolution of Arabidopsis protection of telomeres 1 alters nucleic acid recognition and telomerase regulation.
abstract: Protection of telomeres (POT1) binds chromosome ends, recognizing single-strand telomeric DNA via two oligonucleotide/oligosaccharide binding folds (OB-folds). The Arabidopsis thaliana POT1a and POT1b paralogs are atypical: they do not exhibit telomeric DNA binding, and they have opposing roles in regulating telomerase activity. AtPOT1a stimulates repeat addition processivity of the canonical telomerase enzyme, while AtPOT1b interacts with a regulatory lncRNA that represses telomerase activity. Here, we show that OB1 of POT1a, but not POT1b, has an intrinsic affinity for telomeric DNA. DNA binding was dependent upon a highly conserved Phe residue (F65) that in human POT1 directly contacts telomeric DNA. F65A mutation of POT1aOB1abolished DNA binding and diminished telomerase repeat addition processivity. Conversely, AtPOT1b and other POT1b homologs from Brassicaceae and its sister family, Cleomaceae, naturally bear a non-aromatic amino acid at this position. By swapping Val (V63) with Phe, AtPOT1bOB1gained the capacity to bind telomeric DNA and to stimulate telomerase repeat addition processivity. We conclude that, in the context of DNA binding, variation at a single amino acid position promotes divergence of the AtPOT1b paralog from the ancestral POT1 protein.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843, USA.
authors.forename: Amit
authors.initials: A
authors.lastname: Arora
authors.affiliation: School of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Beilstein
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, 2128 TAMU, College Station, TX 77843, USA dshippen@tamu.edu.
authors.forename: Dorothy E
authors.identifier: http://orcid.org/0000-0003-0562-2047
authors.initials: DE
authors.lastname: Shippen
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D001665:Binding Sites; D005075:Biological Evolution; D017124:Conserved Sequence; D008958:Models, Molecular; D010649:Phenylalanine / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D000089804:Shelterin Complex; D019098:Telomerase / Q000737:chemistry / Q000378:metabolism*; D016615:Telomere / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C503876:Pot1 protein, Arabidopsis; D018749:RNA, Plant; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D010649:Phenylalanine; D019098:Telomerase