Long-range cooperativity in molecular recognition of RNA by oligodeoxynucleotides with multiple C5-(1-propynyl) pyrimidines.
A heptamer composed of C5-(1-propynyl) pyrimidines (Y(p)'s) is a potent and specific antisense agent against the mRNA of SV40 large T antigen (Wagner, R. W.; Matteucci, M. D.; Grant, D.; Huang, T.; Froehler, B. C. Nat. Biotechnol. 1996, 14, 840-844). To characterize the role of the propynyl groups in molecular recognition, thermodynamic increments associated with substitutions in DNA:RNA duplexes, such as 5'-dCCUCCUU-3':3'-rGAGGAGGAAAU-5', have been measured by UV melting experiments. For nucleotides tested, an unpaired dangling end stabilizes unmodified and propynylated duplexes similarly, except that addition of a 5' unpaired rA is 1.4 kcal/mol more stabilizing on the propynylated, PODN:RNA, duplex than on the DNA:RNA duplex. Free energy increments for addition of single propynyl groups range from 0 to -4.0 kcal/mol, depending on the final number and locations of substitutions. A preliminary model for predicting the stabilities of Y(p)-containing hybrid duplexes is presented. Eliminating one amino group, and therefore a hydrogen bond, by substituting inosine (I) for guanosine (G), to give 5'-dC(p)C(p)U(p)C(p)C(p)U(p)U(p)-3':3'-rGAGIAGGAAAU-5', destabilizes the duplex by 3.9 kcal/mol, compared to 1.7 kcal/mol for the same change within the unpropynylated duplex. This 2.2 kcal/mol difference is eliminated by removing a single propynyl group three base pairs away. CD spectra suggest that single propynyl deletions within the PODN:RNA duplex have position-dependent effects on helix geometry. The results suggest long-range cooperativity between propynyl groups and provide insights for rationally programming oligonucleotides with enhanced binding and specificity. This can be exploited in developing technologies that are dependent upon nucleic acid-based molecular recognition.
Barnes
T W
TW
Department of Chemistry, University of Rochester, Rochester, New York 14627-0216, USA.
Turner
D H
DH
D000241:Adenosine / Q000737:chemistry; D002942:Circular Dichroism; D004247:DNA / Q000737:chemistry; D006151:Guanosine / Q000737:chemistry; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D009841:Oligonucleotides / Q000138:chemical synthesis / Q000737:chemistry* / Q000302:isolation & purification; D011743:Pyrimidines / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*; D012044:Regression Analysis; D013816:Thermodynamics; D014466:Ultraviolet Rays
D009841:Oligonucleotides; D011743:Pyrimidines; D006151:Guanosine; D012313:RNA; D004247:DNA; D000241:Adenosine