FIG. 1.

RNA stem-loop structures and stem energies of wild-type and mutated TAR RNA sequences. TAR mutations are shown as follows: 1, 3-nt deletion from position +22 to +24 (TAR1); 2, 6-nt deletion from position +19 to +24 (TAR2); 3, combined 3-nt deletion from position +22 to +24 and compensatory 3-nt insertion of UCU at position +39 (TAR3); 4, three nucleotide substitutions at positions +15, +16, and +18 (TAR4); 5, four nucleotide substitutions at positions +18, +19, +21, and +39 (TAR5); and 6, six nucleotide substitutions, at nt +18, +19, +21, +39, +41, and +42, that maintained the stem-loop structure (TAR6). RNA stem-loop structure energies (ΔG), shown in kilocalories per mole, were predicted using M-fold version 3.0 (copyright 1996 by M. Zuker; http://mfold.burnet.edu.au).