Naturally occurring antisense RNA

Within the last few years a number of mammalian genes have been found for which there exist naturally occurring “antisense” RNA species with complementarity to mRNAs. Effects of antisense RNA on “sense” RNA have yet to be established. Nevertheless, it is apparent that mammalian cells have devoted genetic information and machinery to processing RNA:RNA hybrids, and it is becoming clear that there may be many more genes than previously suspected to which natural antisense RNAs exist. If naturally occurring antisense RNAs are mediators of alterations in gene expression, the question arises as to whether these pathways can be exploited pharmacologically.