TETRAMERIZATION OF AN RNA OLIGONUCLEOTIDE CONTAINING A GGGG SEQUENCE

POLY rG can form four-stranded helices 1. The Hoogsteen-paired quartets of G residues on which such structures depend are so stable that they will form in 5'-GMP solutions, provided that Na+ or K+ are present (see for example, refs 2-4). Telomeric DNA sequences, which are G-rich, adopt four-stranded antiparallel G-quartet conformations in vitro 5,6, and parallel tetramerization of G-rich sequences may be involved in meiosis 7,8. Here we show that RNAs containing short runs of Gs can also tetramerize. A 19-base oligonucleotide derived from the 5S RNA of Escherichia coli (strand III), 5'GCCGAUGGUAGUGUGGGGU3', forms a K+-stabilized tetrameric aggregate that depends on the G residues at its 3' end. This complex is so stable that it would be surprising if similar structures do not occur in nature.