Nucleic Acids Research Advance Access originally published online on October 13, 2006
Nucleic Acids Research 2006 34(20):5740-5751; doi:10.1093/nar/gkl617
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Nucleic Acids Research, 2006, Vol. 34, No. 20 5740-5751
© 2006 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Solution structure of a purine rich hexaloop hairpin belonging to PGY/MDR1 mRNA and targeted by antisense oligonucleotides
1 Laboratoire BioMoCeTi, CNRS UMR 7033 UFR SMBH, Université Paris 13, 74 rue Marcel Cachin, 93017 Bobigny cedex, France 2 Laboratoire de Biochimie Théorique, CNRS UPR 9080 Institut de Biologie Physico-Chimique, 13 rue Pierre et Marie Curie, 75005 Paris, France
*To whom correspondence should be addressed. Tel: +33 158415167; Fax: +33 158415026; Email: fjoli{at}smbh.univ-paris13.fr
Received May 3, 2006. Revised August 6, 2006. Accepted August 7, 2006.
A preferential target of antisense oligonucleotides directed against human PGY/MDR1 mRNA is a hairpin containing a stem with a G•U wobble pair, capped by the purine-rich 5'r(GGGAUG)3' hexaloop. This hairpin is studied by multidimensional NMR and restrained molecular dynamics, with special emphasis on the conformation of south sugars and non-standard phosphate linkages evidenced in both the stem and the loop. The hairpin is found to be highly structured. The G•U wobble pair, a strong counterion binding site, displays structural particularities that are characteristic of this type of mismatch. The upper part of the stem undergoes distortions that optimize its interactions with the beginning of the loop. The loop adopts a new fold in which the single-stranded GGGA purine tract is structured in A-like conformation stacked in continuity of the stem and displays an extensive hydrogen bonding surface for recognition. The remarkable hairpin stability results from classical inter- and intra-strand interactions reinforced by numerous hydrogen bonds involving unusual backbone conformations and ribose 2'-hydroxyl groups. Overall, this work emphasizes numerous features that account for the well-ordered structure of the whole hairpin and highlights the loop properties that facilitate interaction with antisense oligonucleotides.
*Correspondence may also be addressed to Brigitte Hartmann. Tel: +33 158415169; Fax: +33 158415026; Email: brigitte.hartmann{at}ibpc.fr