Transitions between the steps of forward and reverse splicing of group IIC introns

Secondary structure of the Ta.it.I1 group IIC intron. Six RNA secondary structure domains are shown radiating from a central hub. Colors of domains match previously published group II intron crystal structures. Domain IV encodes an ORF that was removed for in vitro ribozyme splicing assays; points of deletion are shown. Greek letters indicate RNA tertiary interactions. Mutation of the putative π tetraloop is shown. Exons are recognized by IBS-EBS elements, γ–γ′, and a terminator stem–loop element.