title: Dynamic peptides of human TPP1 fulfill diverse functions in telomere maintenance.
abstract: Telomeres are specialized nucleoprotein complexes that comprise the ends of linear chromosomes. Human telomeres end in a short, single-stranded DNA (ssDNA) overhang that is recognized and bound by two telomere proteins, POT1 and TPP1. Whereas POT1 binds directly to telomere ssDNA, its interaction with TPP1 is essential for localization of POT1 to the telomere. TPP1 also provides enhanced binding and sequence discrimination that regulates POT1-TPP1 interactions exclusively with telomere ssDNA. Finally, TPP1 recruits telomerase, the enzyme responsible for synthesis of telomere DNA, to the telomere. While the oligosaccharide-oligonucleotide-binding (OB)-fold domain of TPP1 has been solved by X-ray crystallography, the molecular interactions within the POT1-TPP1-ssDNA ternary complex and the conformational changes that contribute to its diverse functions remain ambiguous. We employed hydrogen/deuterium exchange combined with mass spectrometry to identify three peptides, all residing within the OB-fold of TPP1, that exhibit altered exchange rates upon complex formation or ssDNA binding. Mutation of these regions combined with functional assays revealed the diverse contributions of each moiety in protein-protein interactions, regulating telomerase activity or DNA-binding. Together, these functional data combined with biophysical analyses and homology modeling provide a molecular understanding of the diverse contributions of TPP1 in telomere maintenance.
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Malligarjunan
authors.initials: M
authors.lastname: Rajavel
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Tivadar
authors.initials: T
authors.lastname: Orban
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Mengyuan
authors.initials: M
authors.lastname: Xu
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Wilnelly
authors.initials: W
authors.lastname: Hernandez-Sanchez
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Maria
authors.initials: M
authors.lastname: de la Fuente
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Palczewski
authors.affiliation: Department of Pharmacology, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA derek.taylor@case.edu.|Department of Biochemistry, Case Western Reserve University, School of Medicine, Cleveland, OH 44106, USA.
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Taylor
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D013058:Mass Spectrometry; D008958:Models, Molecular; D009154:Mutation; D010455:Peptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D055503:Protein Multimerization; D011993:Recombinant Fusion Proteins; D057057:Serine Proteases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000089804:Shelterin Complex / Q000737:chemistry; D013329:Structure-Activity Relationship; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000378:metabolism*; D059505:Telomere Homeostasis / Q000187:drug effects; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C495876:ACD protein, human; D010455:Peptides; D011993:Recombinant Fusion Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D004247:DNA; D019098:Telomerase; D057057:Serine Proteases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases