[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.

[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.

[Dimerization of short RNA fragments from avian leukosis virus as revealed with 2-aminopurine fluorescence].

The dimerization of genomic retroviral RNA is well studied for several groups of viruses, the dimerization of human immunodeficiency (HIV) RNA being investigated in more detail. Regions of dimerization apparently involve the short sequences RNA which are directly responsible for the formation of two type dimers: kissing loop-loop (KD) and linear (LD). The 5'-end sequences from RNA avian viruses, where the dimers are basically formed, considerably differ from those of HIV.

[Characteristic of the two-step RNA dimerization in avian sarcoma and leukosis viruses].

Dimerization of two copies of genomic RNA is a necessary step of retroviral replication. In the case of human immunodeficiency virus type 1 (HIV-1) the process is explored in many details. It is proved that conserved stem-loop structure is an essential element in RNA dimerization.

[The role of structural elements in dimerization of RNA fragments in avian retroviruses].

The slipped loop structure, earlier identified as an unusual DNA structure, was found to be a possible element of the RNA folding. In order to experimentally test this suggestion, model oligoribonucleotides capable of forming the SLS were synthesized. Treatment of the oligoribonucleotides with nuclease S1 and RNases specific for single- and double-stranded RNA demonstrated the steric possibility of SLS formation.

[Why termination tRNAs have not been found? Because they are hidden in the large ribosomal RNA].

It is well known that protein synthesis in ribosomes on mRNA requires two kinds of tRNAs: initiation and elongation. The former initiates the process (formylmethionine tRNA in prokaryotes and special methionine tRNA in eukaryotes). The latter participates in the synthesis proper, recognizing the sense codons.

[The Z-form of DNA. Nonmonotonous change in stability with increase in ionic strength].

To specify the stability area of the Z-DNA conformation as a function of ambient conditions (ionic strength, temperature, water activity) a 3-D phase diagram for the (B,Z) equilibrium as exemplified by poly(dG-5ethyldC) has been constructed in experiment. Its main peculiarity proves to be the nonmonotonic change in stability of the Z form with ionic strength, with a minimum at 0.1 M NaCl, i.

[SLS--a new type of polynucleotide chain folding].

Short tandem repeats (5-8 base pairs) are not uncommon in the prokaryotic and eukaryotic DNA. Regions with such sequence motifs, when under superhelical stress, manifest unusual sensitivity to single-strand specific nuclease. To explain this, it has been suggested that one DNA thread should be shifted relatively to another, so that they could form two single-stranded loops protruding from the opposite chains and separated on the DNA helix by the length of a direct repeat.

[Study of cooperative transitions in DNA using phase diagrams].

The study of the triple equilibria (A, B, Coil) and (A, B, Z) makes it possible to obtain interconnection between thermodynamic parameters of different co-operative transitions in DNA. Melting of DNA of poly[d(A--T)] was performed in a broad interval of trifluoroethanol (TFE) concentrations including those of the B to A transition range. A branch, which characterizes the helix-coil equilibrium, has a universal shape for different DNAs and the polynucleotide: melting temperature is minimum near 30% TFE and increases sharply within the region of the A form stability (greater than 65% TFE).