[The interaction of dimeric form of RNA retroviruses with paromomycin and magnesium: using the fluorescence of 2-aminopurine].

The studying of the dimeric RNA structural organization is a step in the understanding of retroviruses genomic RNA dimerization. The RNA kissing loop dimer rearrangement into the extended dimer occurs during the maturation of virus particle. The inhibition of the extended dimerformation can be caused by ligands interaction with RNA kissing loop dimer. Here, we study the interaction of the dimeric RNA with paromomycin and magnesium ions. RNA dimers were formed from the different hairpin RNA having the complementary sequences in the loop. To detect the structural features of RNA dimers and influence of the ligands we used the 2-aminopurine fluorescence (2-AP) incorporated in one of two RNA hairpin sequences. It was observed that the 2-AP fluorescence increases under dimer RNA interaction with paromomycin. The growing of 2-AP fluorescence can be explaining by fluorescent base flipping out from the RNA structure. The binding affinity and stoichiometry to the kissing loop a nd extended dimers were found by2-AP fluorescence alteration. It turned out, that one RNA dimer binds with two paromomycin molecules; the binding constants for both dimers type were approximately the same and about 3 x 10(5) M(-1). The competition of antibiotic and Mg2+ ions binding were revealed. It was found that one paromomycin molecules displaced by one Mg2+ ion.

[The influence of aminoglycoside antibiotics on the conformation of the unpairing loop adenine of avian leukosis virus RNA as revealed with 2-aminopurine fluorescence].

Fluorescent properties of 2-aminopurine included in the sequence RNA, are now used for the study of structural dynamics and local changes of structure retroviral RNA. We used 2-aminopurine for studying the conformational states of unpaired loop adenine of avian leukosis virus RNA upon the interaction with the aminoglycoside antibiotics. It was shown, that intensity of 2-aminopurine fluorescence for monomer hairpin RNA has greater value in comparison with both RNA dimers. Comparing the 2-aminopurine fluorescence of RNA dimers, it has found out that the intensity of fluorescence for extended dimer significantly lower than the kissing loop dimer RNA. This can be explained by the fact that the stacking contacts forms more compact structure of a loop in extended dimer concerning those in structure of kissing loop dimer. When the binding of aminogycoside antibiotics with kissing loop dimer RNA it was observed that only the tobramycin increases nearly three times the intensity of 2-aminopurine fluorescence. Results of work testify that it is possible to detect local changes in the complexes of retroviral RNA with ligands, using the fluorescence 2-aminopurine.