title: Nonadditivity in the recognition of single-stranded DNA by the schizosaccharomyces pombe protection of telomeres 1 DNA-binding domain, Pot1-DBD.
abstract: The Schizosaccharomyces pombe protection of telomeres 1 (SpPot1) protein recognizes the 3' single-stranded ends of telomeres and provides essential protective and regulatory functions. The ssDNA-binding activity of SpPot1 is conferred by its ssDNA-binding domain, Pot1-DBD (residues 1-389), which can be further separated into two distinct domains, Pot1pN (residues 1-187) and Pot1pC (residues 188-389). Here we show that Pot1pC, like Pot1pN, can function independently of Pot1-DBD and binds specifically to a minimal nonameric oligonucleotide, d(GGTTACGGT), with a K(D) of 400 +/- 70 nM (specifically recognized nucleotides in bold). NMR chemical shift perturbation analysis indicates that the overall structures of the isolated Pot1pN and Pot1pC domains remain intact in Pot1-DBD. Furthermore, alanine scanning reveals modest differences in the ssDNA-binding contacts provided by isolated Pot1pN and within Pot1-DBD. Although the global character of both Pot1pN and Pot1pC is maintained in Pot1-DBD, chemical shift perturbation analysis highlights localized structural differences within the G1/G2 and T3/T4 binding pockets of Pot1pN in Pot1-DBD, which correlate with its distinct ssDNA-binding activity. Furthermore, we find evidence for a putative interdomain interface on Pot1pN that mediates interactions with Pot1pC that ultimately result in the altered ssDNA-binding activity of Pot1-DBD. Together, these data provide insight into the mechanisms underlying the activity and regulation of SpPot1 at the telomere.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, Colorado 80309-0215, USA.
authors.forename: Johnny E
authors.initials: JE
authors.lastname: Croy
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Altschuler
authors.forename: Nicole E
authors.initials: NE
authors.lastname: Grimm
authors.forename: Deborah S
authors.initials: DS
authors.lastname: Wuttke
mesh_terms: D004277:DNA, Single-Stranded / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D008958:Models, Molecular; D016296:Mutagenesis; D019906:Nuclear Magnetic Resonance, Biomolecular; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D016615:Telomere
chemical_list: D004277:DNA, Single-Stranded; D029702:Schizosaccharomyces pombe Proteins