title: DNA binding features of human POT1: a nonamer 5'-TAGGGTTAG-3' minimal binding site, sequence specificity, and internal binding to multimeric sites.
abstract: The human telomeric protein POT1 is known to bind single-stranded telomeric DNA in vitro and to participate in the regulation of telomere maintenance by telomerase in vivo. We examined the in vitro DNA binding features of POT1. We report that deleting the oligosaccharide/oligonucleotide-binding fold of POT1 abrogates its DNA binding activity. The minimal binding site (MBS) for POT1 was found to be the telomeric nonamer 5'-TAGGGTTAG-3', and the optimal substrate is [TTAGGG](n (n > or = 2)). POT1 displays exceptional sequence specificity when binding to MBS, tolerating changes only at position 7 (T7A). Whereas POT1 binding to MBS or [TTAGGG](2) was enhanced by the proximity of a 3' end, POT1 was able to bind to a [TTAGGG](5) array when positioned internally. These data indicate that POT1 has a strong sequence preference for the human telomeric repeat tract and predict that POT1 can bind both the 3' telomeric overhang and the displaced TTAGGG repeats at the base of the t-loop.
authors.affiliation: Laboratory for Cell Biology and Genetics, The Rockefeller University, 1320 York Avenue, New York, NY 10021, USA.
authors.forename: Diego
authors.initials: D
authors.lastname: Loayza
authors.forename: Heather
authors.initials: H
authors.lastname: Parsons
authors.forename: Jill
authors.initials: J
authors.lastname: Donigian
authors.forename: Kristina
authors.initials: K
authors.lastname: Hoke
authors.forename: Titia
authors.initials: T
authors.lastname: de Lange
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000737:chemistry; D018076:DNA, Complementary / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D007313:Insecta; D007700:Kinetics; D009841:Oligonucleotides / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D009841:Oligonucleotides; C440849:POT1 protein, human; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; D004247:DNA; D005982:Glutathione Transferase