FIGURE 1.

Folded secondary structure of M. jannaschii sR8 box C/D RNA, a model archaeal box C/D sRNA. The spacing between the box C/D and C′/D′ motifs in archaeal box C/D sRNAs is conserved. Consensus sequence elements (boxes C and D of the terminal core motif and internal boxes C′ and D′) are indicated in bold lettering. The spacer regions between boxes C and D′ (D′ spacer) and boxes C′ and D (D spacer) are designated. These spacer regions include, but are not limited to, the sRNA guide sequence that base pairs with the respective target RNAs. Bold arrows indicate the sites of nucleotide insertions and deletions for the constructed sR8 sRNA mutants.