RNA STRUCTURE AND THE REGULATION OF GENE-EXPRESSION

RNA secondary and tertiary structure is involved in post-transcription al regulation of gone expression either by exposing specific sequences or through the formation of specific structural motifs. An overview o f RNA secondary and tertiary structures known from biophysical studies is followed by a review of examples of the elements of RNA processing , mRNA stability and translation of the messenger. These structural el ements comprise sense-antisense double-stranded RNA, hairpin and stem- loop structures, and more complex structures such as bifurcations, pse udoknots and triple-helical elements. Metastable structures formed dur ing RNA folding pathway are also discussed. The examples presented are mostly chosen from plant systems, plant viruses, and viroids. Example s from bacteria or fungi are discussed only when unique regulatory pro perties of RNA structures have been elucidated in these systems.