Figure 2.

Schematic of self-processing (cleavage and ligation) of the RNA Lasso precursor. Self-processing of a primary Lasso transcript (pre-Lasso) having 5′-triphosphate (5′-PPP) and 3′-hydroxyl (3′-OH) groups can proceed by either the right or left pathway. Self-cleavage catalyzed by the HPR generates specific fragments having 2′,3′-cyclic phosphate (2′,3′ > P) and 5′-hydroxyl (5′-OH) termini. The fully 5′- and 3′-processed RNA Lasso exists as an equilibrium between circular and linear forms. The cleavage/ligation sites are marked by magenta arrows with asterisks. Loops 1, 2 or 3 indicated in the bottom structure can be used for insertion of an antisense sequence. Here, the antisense sequence (red) is inserted into loop 2 (blue). Species are identified as unprocessed Lasso (UPL), 5′-half-processed Lasso (5′-HPL), 3′-half-processed Lasso (3′-HPL), 5′- and 3′-processed ‘linear’ Lasso (LL) and circular Lasso (CL).