Sequence-dependence of the conformational changes induced by the 5-methyl cytosine in synthetic RNA oligomers.

The RNA hexamer containing a 5-methyl cytosine (m5C) r(CGUAm5CG) was studied by 1H and 31P NMR at 500 MHz and 121 MHz, respectively. In contrast to r(CGm5CGCG) which exhibits an atypic duplex structure [(1987) J. Am. Chem. Soc. 109, 2539-2541], r(CGUAm5CG) adopts a classical A-type conformation. This result demonstrates that the influence of the m5C on the conformation of RNA hexamers is sequence-dependent.