Biosynthesis and structure of stable branched RNA covalently linked to the 5′ end of multicopy single-stranded DNA of Stigmatella aurantiaca

Abstract

Stigmatella aurantiaca, a gram-negative bacterium, contains approximately 500 copies per cell of a short single-stranded linear DNA (multicopy single-stranded DNA: msDNA). This DNA is attached to a branched RNA (msdRNA) by its 5′ end. The entire sequence of msdRNA was determined and found to consist of 76 bases. The msDNA is linked at the 19th G residue of msdRNA by a 2′, 5′ phosphodiester linkage. The coding region for msdRNA ( msr) is located downstream of the coding region for msDNA ( msd). These coding regions exist in opposite orientation with respect to each other and overlap by 8 bases at their 3′ ends. Biosynthesis of RNA-linked msDNA was characterized and mechanisms of synthesis are proposed.