Branched RNA covalently linked to the 5′ end of a single-stranded DNA in Stigmatella aurantiaca: Structure of msDNA

Abstract

Stigmatella aurantiaca is a gliding, gram-negative bacterium that shows a spectacular fruiting body formation upon starvation of nutrient. This bacterium was found to contain approximately 500 copies per cell of a short single-stranded linear DNA (multicopy single-stranded DNA: msDNA). The primary structure of msDNA was determined and found to consist of 162 or 163 deoxyrlbonucleotides. Its unique chromosomal gene was cloned and sequenced. The msDNA was found to be attached to a branched RNA by its 5′ end. Structural analysis of the branched RNA revealed that it consists of a triribonucleotide, 5′A-G-(C or U) 3′, and that msDNA is branched out from the 2′ position of the rG residue forming a 2′, 5′ phosphodiester linkage with the dC residue at the 5′ end of msDNA.