title: The effect of Pot1 binding on the repair of thymine analogs in a telomeric DNA sequence.
abstract: Telomeric DNA can form duplex regions or single-stranded loops that bind multiple proteins, preventing it from being processed as a DNA repair intermediate. The bases within these regions are susceptible to damage; however, mechanisms for the repair of telomere damage are as yet poorly understood. We have examined the effect of three thymine (T) analogs including uracil (U), 5-fluorouracil (5FU) and 5-hydroxymethyluracil (5hmU) on DNA-protein interactions and DNA repair within the GGTTAC telomeric sequence. The replacement of T with U or 5FU interferes with Pot1 (Pot1pN protein of Schizosaccharomyces pombe) binding. Surprisingly, 5hmU substitution only modestly diminishes Pot1 binding suggesting that hydrophobicity of the T-methyl group likely plays a minor role in protein binding. In the GGTTAC sequence, all three analogs can be cleaved by DNA glycosylases; however, glycosylase activity is blocked if Pot1 binds. An abasic site at the G or T positions is cleaved by the endonuclease APE1 when in a duplex but not when single-stranded. Abasic site formation thermally destabilizes the duplex that could push a damaged DNA segment into a single-stranded loop. The inability to enzymatically cleave abasic sites in single-stranded telomere regions would block completion of the base excision repair cycle potentially causing telomere attrition.
authors: Department of Pharmacology and Toxicology, The University of Texas Medical Branch, 3.330 Basic Science Building, 301 University Blvd, Galveston, TX 77555-0617, USA.
authors: Jacob A
authors: JA
authors: Theruvathu
authors: Department of Pharmacology and Toxicology, The University of Texas Medical Branch, 3.330 Basic Science Building, 301 University Blvd, Galveston, TX 77555-0617, USA.
authors: Agus
authors: A
authors: Darwanto
authors: Department of Pharmacology and Toxicology, The University of Texas Medical Branch, 3.330 Basic Science Building, 301 University Blvd, Galveston, TX 77555-0617, USA.
authors: Chia Wei
authors: CW
authors: Hsu
authors: Department of Pharmacology and Toxicology, The University of Texas Medical Branch, 3.330 Basic Science Building, 301 University Blvd, Galveston, TX 77555-0617, USA lasowers@utmb.edu.
authors: Lawrence C
authors: LC
authors: Sowers
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism; D005472:Fluorouracil / Q000737:chemistry / Q000378:metabolism; D010432:Pentoxyl / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D000089804:Shelterin Complex; D016615:Telomere / Q000737:chemistry* / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000378:metabolism*; D014498:Uracil / Q000737:chemistry* / Q000378:metabolism; D051981:Uracil-DNA Glycosidase / Q000378:metabolism
chemical_list: D029702:Schizosaccharomyces pombe Proteins; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins; C499082:pot1 protein, S pombe; C008055:5-hydroxymethyluracil; D014498:Uracil; D010432:Pentoxyl; D004247:DNA; D051981:Uracil-DNA Glycosidase; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D005472:Fluorouracil