FIELD: molecular biology, organic chemistry. SUBSTANCE: oligonucleotide has phosphorothioate and/or phosphorodithioate bonds and involves deoxyribonucleoside, ribonucleoside or 2'-substituted ribonucleoside. In therapeutic composition effective amount of oligonucleotide showing the sequence that is complementary to nucleic acid sequence of virus, pathogenic organism or cellular gene is used in combination with pharmaceutically acceptable carrier. Oligonucleotide has phosphorothioate and/or phosphorodithioate bonds and deoxyribonucleoside, ribonucleoside or 2'-substituted ribonucleoside also. Synthesized hybrid oligonucleotide ensures to regulate gene expression effectively. Oligonucleotide can be used in gene expression investigations and for therapy purposes also. EFFECT: improved method of synthesis, enhanced effectiveness of oligonucleotide and gene expression regulation. 12 cl, 4 dwg, 3 tbl, 5 ex
