Molecular dynamics simulations and coupled nucleotide substitution experiments indicate the nature of A{middle dot}A base pairing and a putative structure of the coralyne-induced homo-adenine duplex.
Coralyne is an alkaloid drug that binds homo-adenine DNA (and RNA) oligonucleotides more tightly than it does Watson-Crick DNA. Hud's laboratory has shown that poly(dA) in the presence of coralyne forms an anti-parallel duplex, however attempts to determine the structure by NMR spectroscopy and X-ray crystallography have been unsuccessful. Assuming adenine-adenine hydrogen bonding between the two poly(dA) strands, we constructed 40 hypothetical homo-(dA) anti-parallel duplexes and docked coralyne into the six most favorable duplex structures. The two most stable structures had trans glycosidic bonds, but distinct pairing geometries, i.e. either Watson-Crick Hoogsteen (transWH) or Watson-Crick Watson-Crick (transWW) with stability of transWH > transWW. To narrow down the possibilities, 7-deaza adenine base substitutions (dA-->7) were engineered into homo-(dA) sequences. These substitutions significantly reduced the thermal stability of the coralyne-induced homo-(dA) structure. These experiments strongly suggest the involvement of N7 in the coralyne-induced A.A base pairs. Moreover, due to the differential effect on melting as a function of the location of the dA-->7 mutations, these results are consistent with the N1-N7 base pairing of the transWH pairs. Together, the simulation and base substitution experiments predict that the coralyne-induced homo-(dA) duplex structure adopts the transWH geometry.
Joung
In Suk
IS
Department of Bioengineering, College of Engineering, University of Utah, Salt Lake City, UT 84112, USA.
Persil Cetinkol
Ozgül
O
Hud
Nicholas V
NV
Cheatham
Thomas E
TE
D020029:Base Pairing; D001600:Berberine Alkaloids / Q000737:chemistry*; D004247:DNA / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry*; D007364:Intercalating Agents / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D012997:Solvents / Q000737:chemistry; D014372:Tubercidin / Q000737:chemistry
D001600:Berberine Alkaloids; D003839:Deoxyadenosines; D007364:Intercalating Agents; D012997:Solvents; C000666:coralyne; D004247:DNA; D014372:Tubercidin