Nucleic Acids Research, Vol 26, Issue 6 1509-1514, Copyright © 1998 by Oxford University Press
M Vorlickova, I Kejnovska, J Kovanda and J Kypr
CD spectroscopy and PAGE were used to cooperatively analyze melting
conformers of DNA strands containing GA and TA dinucleotide repeats. The
20mer (GA)10 formed a homoduplex in neutral solutions containing
physiological concentrations of salts and this homoduplex was not
destabilized even in the terminal (GA)3 hexamers of (GA)3(TA)4(GA)3,
although the central (TA)4 portion of this oligonucleotide preserved the
conformation adopted by (TA)10. This observation demonstrates that
homoduplexes of alternating GA and TA sequences can co-exist in a single
DNA molecule. Another 20mer, (GATA)5, adopted as a whole either the AT
duplex, like (TA)10, or the GA duplex, like (GA)10, and switched between
them reversibly. The concentration of salt controlled the conformational
switching. Hence, guanine and thymine share significant properties
regarding complementarity to adenine, while the TA and GA sequences can
stack in at least two mutually compatible ways within the DNA duplexes
analyzed here. These properties extend our knowledge of non-canonical
structures of DNA.
ARTICLES
Conformational properties of DNA strands containing guanine-adenine and thymine-adenine repeats
Institute of Biophysics, Academy of Sciences of the Czech Republic, Kralovopolska 135, CZ-612 65 Brno, Czech Republic. mifi@ibp.cz
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