title: C5-methylation of cytosine in B-DNA thermodynamically and kinetically stabilizes BI.
abstract: We have examined the backbone dynamics of two alternating purine-pyrimidine dodecamers. One sequence consists of "pure" GC bases; the other one contains 5-methylcytosines. The effect of the methyl groups on the backbone substates BI/BII was investigated by means of molecular dynamics. The methylation influences, on one hand, the transition barrier between BI and BII and, on the other hand, the state of equilibrium. The kinetic consequences are an increase of the DeltaG of Gp5mC steps by 1.5 kcal/mol and a decrease of the DeltaG of 5mCpG steps by 0.8 kcal/mol (compared with the nonmethylated DNA). Thus, the additive group differentiates between the two occurring dinucleotide steps and renders the phosphate of the 5-methylcytosine more rigid, as proposed by experimental studies. The thermodynamic consequences are an increase of the DeltaG of Gp5mC steps by 1.1 kcal/mol and a decrease of the DeltaG of 5mCpG steps by 0.8 kcal/mol. The reason for this shift in equilibrium is still not completely clear on a molecular basis. But we can conclude that the indirect readout of DNA is influenced by methylation.
authors.affiliation: Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, 6020 Innsbruck, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Rauch
authors.forename: Michael
authors.initials: M
authors.lastname: Trieb
authors.forename: Bernd
authors.initials: B
authors.lastname: Wellenzohn
authors.forename: Markus
authors.initials: M
authors.lastname: Loferer
authors.forename: Andreas
authors.initials: A
authors.lastname: Voegele
authors.forename: Fajar R
authors.initials: FR
authors.lastname: Wibowo
authors.forename: Klaus R
authors.initials: KR
authors.lastname: Liedl
mesh_terms: D003198:Computer Simulation; D003596:Cytosine / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D019175:DNA Methylation; D007700:Kinetics; D009690:Nucleic Acid Conformation; D013816:Thermodynamics
chemical_list: D003596:Cytosine; D004247:DNA