Structural influence of RNA incorporation in DNA: quantitative nuclear magnetic resonance refinement of d(CG)r(CG)d(CG) and d(CG)r(C)d(TAGCG).
RNA and DNA adopt different types of conformations, i.e., A-type with C3'-endo sugar pucker for RNA and B-type with C2'-endo sugar pucker for DNA, respectively. The structural influence of the incorporation of RNA nucleotides into DNA is less understood. In this paper, we present the three-dimensional structures of two RNA-containing oligonucleotides, d(CG)r(CG)d(CG) and d(CG)r(C)d-(TAGCG), as determined by the NMR refinement procedure, and assess the possible structural perturbation of DNA induced by RNA. With a single RNA insertion into an octamer DNA, its overall conformation remains as the canonical B-DNA, except that the sugar pucker of the rC3 residue is C3'-endo (pseudorotation angle P = 3.6 degrees). In contrast, the hybrid hexamer is neither the pure B-DNA nor the pure A-DNA conformation. Instead, we propose a model in which the DNA parts adopt B conformation, whereas the RNA part adopts A conformation, with the overall conformation closer to A-DNA. To ensure an exhaustive search of the conformational space, the model was subjected to 100-ps simulated annealing with slow cooling or 100-ps molecular dynamics with subsequent quenching. Models obtained at different time points of the trajectories were further subjected to the SPEDREF NOE refinement [Robinson & Wang (1992) Biochemistry 31, 3524] and they appeared to arrive at a convergent model (< 0.5 A RMSD for the central four base pairs). The consensus hexamer structure contains a significant discontinuity at the (rG4)p(dC5) step with a base pair tilt angle of 6.7 degrees and roll angle of 11.5 degrees.(ABSTRACT TRUNCATED AT 250 WORDS)
Jaishree
T N
TN
Biophysics Division, University of Illinois, Urbana-Champaign 61801.
van der Marel
G A
GA
van Boom
J H
JH
Wang
A H
AH
D003080:Cold Temperature; D004247:DNA / Q000737:chemistry*; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D008432:Mathematical Computing; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009691:Nucleic Acid Denaturation; D009693:Nucleic Acid Hybridization; D009841:Oligonucleotides / Q000737:chemistry*; D011066:Poly C / Q000737:chemistry; D011068:Poly G / Q000737:chemistry; D011089:Polydeoxyribonucleotides / Q000737:chemistry; D012313:RNA / Q000737:chemistry*
D009841:Oligonucleotides; D011089:Polydeoxyribonucleotides; D011068:Poly G; D011066:Poly C; D012313:RNA; D004247:DNA