Influence of specific mutations on the thermal stability of the td group Iintron in vitro and on its splicing efficiency in vivo: A comparative study

Group I introns constitute excellent systems for analyzing the relationship between RNA tertiary folding and catalysis. Within a hierarchical framewor k interpretation of RNA folding, secondary structure motifs subtend RNA thr ee-dimensional (3D) architecture. Thus, mutations in two-dimensional motifs are expected to have effects different from those disrupting 3D contacts. Using UV spectroscopy, we have studied the influence of nucleotide substitu tions, in both secondary and tertiary structure elements, on the thermal st ability of the tertiary folding of the bacteriophage T4 td group I intron. Further, we present a quantitative analysis of the relationship between the splicing efficiency in vivo and the stability of the intron structure as m onitored by UV melting curves. We conclude that the stability of the tertia ry structure of a group I intron as measured by UV melting is generally a g ood indication of its ability to splice in vivo.