Rearrangement of a 1,3-trans-{Pt(NH_3)_2[(GXG)-N7G,N7G]} intrastrand cross-link into interstrand cross-links within RNA duplexes

摘要

The cross-linking reaction described previously in the DNA and 2'-O-methyl RNA series is extended to RNA duplexes. A 17mer single-stranded RNA containing the 1,3-trans-{Pt(NH_3)_2[(GAG)-N7G,N7G]} intrastrand chelate, named G~*AG~* (~* indicating a platinated base) gives, upon pairing with the complementary RNA strand, the G~*AG/CUC~8 interstrand cross-link. The rate of the reaction in 200 mM NaClO_4 is similar to that observed for DNA-RNA duplexes. It depends on the added Na~+ or Mg~(2+) cation and on its concentration. RNA duplexes containing GA/GA or AG/AG tandem mismatches in the rearrangement triplet core were also studied. The major interstrand cross-links, G~*AG/CGA~* and G~*AG/AGC~*, are accompanied by a minor one involving the central G of the CGA or AGC complementary sequence G~*AG/CG~*A and G~*AG/AG~*C. In 200 mM NaClO_4, the G~*A/GA tandem mismatch does not modify the rate of the cross-linking rearrangement whereas the AG~*/AG mismatch slows it down by a factor of four. Our results reflect the predominance of the local structure of the rearrangement core over the nucleophility of the cross-linking base. They also show that the reaction could be used to trap tertiary structures of naturally occurring RNAs, including those with the commonly encountered GA/GA mismatch.