Sequence-specific Solution Structures of the Four Isosequential Pairs of Single-stranded DNAs and RNAs
2008 (English)In: Nature PrecedingsArticle in journal (Other academic) Published
The role of the sequence-context in the self-organization of four single-stranded (ss) isosequential pairs of DNAs (1 – 4) and RNAs (5 – 8), [d/r-(5’C1A2X3G4Y5A6C7): X3 = A or C, Y5 = A or C; sequence variations: 22 = 4], has been elucidated by NMR-constrained Molecular Dynamics (MD) simulations (2 ns). Following sequence-specific observations have been made from the solution NMR and the NMR constrained MD simulation study: (i) Analysis of the NOESY footprints, mainly (H8/H6)n to (H1’ and H3’)n-1 contacts, of ssDNAs (1 – 4) and ssRNAs (5 – 8) in the aqueous medium have shown that all ssDNAs (1 – 4) and ssRNAs (5 – 8) adopt right handed stacked helical structures in the NMR time scale. (ii) Intra-residual cross-peak intensities for the H(8/6)n- H(1’/2’/2’’/H3’)n contacts in ssDNAs and ssRNAs are stronger at the 3’-ends in comparison with those at the 5’-ends, suggesting that the dynamics of the nucleobases at the 3’-end are more restricted, whereas those at the 5’-end are more flexible. (iii) This relative NMR found mobility is consistent with the final RMSd calculations of the final NMR-MD structures of ssDNAs and ssRNAs. They show that the 5’-end nucleobases have higher RMSd values compared to those at the 3’-end, except for the sequence d/r(5’C1A2A3G4A5A6C7). (iv) Relative nOe intensities of inter-residual H(8/6)n – H(1’)n-1 and H(8/6)n – H(3’)n-1 contacts, as well as NMR observed fluctuations in the sugar conformations, for ssDNAs (1 – 4) and ssRNAs (5 – 8) show that no ssDNA or ssRNA adopts either a typical B-type DNA or A-type RNA form. (v) In the final NMR-MD structures all the [H8/6N(n)—H1’N(n-1)/ H3’N(n-1), N = A, G, C] distances in different isosequential pairs of ssDNA (1 – 4) and ssRNA (5 – 8) change depending upon the sequence context of the single-stranded nucleic acids. Both in the deoxy and ribo series, it is the purine-rich sequences [d/r-(5’C1A2A3G4A5A6C7) which form the most stable self-organized right-handed helical structures because of the favorable purine-purine stacking interactions. (vi) Stacking pattern at each of the dinucleotide steps show that the base-base nearest neighbor stacking interactions depend solely upon the sequence contexts of the respective ssDNAs (1 – 4) and ssRNAs (5 – 8). See pages 47 – 145 for Supplementary Information for detailed spectroscopic data.
Place, publisher, year, edition, pages
IdentifiersURN: urn:nbn:se:uu:diva-106717OAI: oai:DiVA.org:uu-106717DiVA: diva2:225937