Control by Antisense RNA

Abstract

Antisense RNAs are small, diffusible, untranslated RNAs that pair to complementary regions on specific target RNAs, altering the expression or function of those RNAs post-transcriptionally. Antisense RNA control is well documented in bacteria, especially in their accessory elements—plasmids, bacteriophages and transposable elements (see Table 5.1). In all of these cases, control is negative. However, mechanisms for positive control are quite plausible. The biological processes inhibited vary widely, as do the mechanisms by which antisense RNAs inhibit those processes. Some antisense RNAs bind directly at their sites of action, while others bind at a distance, altering target RNA structure at the actual site of action. Accessory proteins are involved in a few instances. In most cases, the antisense and target RNAs are transcribed from opposite strands of the same DNA segment and thus contain regions of complete complementarity. In a growing number of cases, however, the antisense and target RNAs are expressed from unlinked genes and complementarity is substantial but incomplete. Antisense RNAs usually contain one or more stem-loop structures. The loop domains are often found to be important determinants of specificity for antisense/target RNA pairing. The stem domains frequently determine metabolic stability.