TRIPLE HELICES CONTAINING ARABINONUCLEOTIDES IN THE 3RD (HOOGSTEEN) STRAND - EFFECTS OF INVERTED STEREOCHEMISTRY AT THE 2'-POSITION OF THE SUGAR MOIETY

Arabinonucleic acid, the 2'-stereoisomer of RNA, was tested for its ab ility to recognize double-helical DNA, double-helical RNA and RNA-DNA hybrids. A pyrimidine oligoarabinonucleotide (ANA) was shown to form t riple-helical complexes only with duplex DNA and hybrid DNA (Pu):RNA ( Py) with an affinity that was slightly lower relative to the correspon ding pyrimidine oligodeoxynucleotide (DNA) third strand. Neither the A NA nor DNA third strands were able to bind to duplex RNA or hybrid RNA (Pu):DNA (Py), In contrast, an RNA third strand recognized all four p ossible duplexes (DD, DR, RD and RR), as previously demonstrated. Such an understanding can be applied to the design of sequence-selective o ligonucleotides which interact with double-stranded nucleic acids and emphasizes the role of the 2'-OH group as a general recognition and bi nding determinant of RNA.