title: Stabilization of triple-helical nucleic acids by basic oligopeptides.
abstract: Intermolecular triplex DNA is stabilized by metal cations and polyamines which reduce repulsion between the negatively charged phosphates of the three nucleic acid strands. We use a quantitative chemical-probing assay involving protection of duplex guanines in a homopyrimidine.homopurine (Py.Pu) sequence from dimethyl sulfate modification to study effects of basic oligopeptides on the stability of triplex DNA. An intermolecular protonated pyrimidine.purine.pyrimidine (Py.Pu*Py) triplex formed readily between a duplex DNA region and a 14-mer pyrimidine triplex-forming oligonucleotide (TFO) at pH 5. The triplex was stabilized at pH by the addition of magnesium ions. In the presence of spermine and lysine-rich peptides, the intermolecular triplex was stabilized up to pH 6.5-7.0. The effective peptide concentration required for stabilization was 10(-5)-10(-2) M. Of the basic peptides studied, pentalysine (Lys-Lys-Lys-Lys-Lys) was the most effective triplex stabilizer. It was effective at concentrations which are lower than those required for Lys-Gly-Lys-Gly-Lys and Lys-Ala-Lys-Ala-Lys and are similar to active concentrations of spermine. Basic peptides were more effective at stabilizing a Py.Pu*Py triplex than a pyrimidine.purine.purine (Py.Pu*Pu) triplex. At 1 mM, Lys-Lys-Lys-Lys-Lys stabilized the Py.Pu*Pu triplex at a level comparable to stabilization by Mn2+ and spermine, whereas Lys-Gly-Lys-Gly-Lys and Lys-Ala-Lys-Ala-Lys resulted in weaker TFO binding. The concentration of TFOs required to form triplex DNA were significantly reduced in the presence of peptides.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Institute of Biosciences and Technology, Texas A&M University, Houston 77030-3303, USA.
authors.forename: V N
authors.initials: VN
authors.lastname: Potaman
authors.forename: R R
authors.initials: RR
authors.lastname: Sinden
mesh_terms: D000477:Alkylating Agents / Q000494:pharmacology; D000595:Amino Acid Sequence; D001483:Base Sequence; D002412:Cations / Q000494:pharmacology; D004247:DNA / Q000737:chemistry*; D006147:Guanine / Q000737:chemistry; D008345:Manganese / Q000494:pharmacology; D008670:Metals / Q000494:pharmacology; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009838:Oligodeoxyribonucleotides / Q000737:chemistry; D009842:Oligopeptides / Q000737:chemistry / Q000494:pharmacology*; D011073:Polyamines / Q000494:pharmacology; D011107:Polylysine / Q000494:pharmacology; D013096:Spermine / Q000494:pharmacology; D013463:Sulfuric Acid Esters / Q000494:pharmacology
chemical_list: D000477:Alkylating Agents; D002412:Cations; D008670:Metals; D009838:Oligodeoxyribonucleotides; D009842:Oligopeptides; D011073:Polyamines; D013463:Sulfuric Acid Esters; C051802:triplex DNA; D011107:Polylysine; D013096:Spermine; D008345:Manganese; D006147:Guanine; D004247:DNA; C007482:dimethyl sulfate