Identification of Aptamers Against the DNA Template for In Vitro Transcription of the HIV-1 TAR Element

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Abstract
We have extracted from a random population of about 109 oligodeoxynucleotides a series of 21-mers that are able to bind to a folded DNA 76-mer used as a template for in vitro transcription of the TAR element of the retrovirus HIV-1, by the T7 RNA polymerase. Five aptastrucs, that is, aptamers able to bind to the structure, out of 15 analyzed sequences, share the consensus motif 5‵-PyGGG(TG)PyC, complementary in part to a weak double-stranded region of the target. (The parentheses indicate that either T or G is missing in one of these aptastrucs.) A dissociation constant of about 3 μM was evaluated by electrophoretic mobility shift assay for the winner sequence. Interactions between the aptastruc and the target sequences involve more than Watson-Crick base pairing of the consensus octamer. The binding is chemistry dependent. Phosphorothioate oligodeoxyribonucleotides and 2‵-O-methyl oligoribonucleotides derived from the selected aptastrucs exhibit a weak if any affinity for the target.