Complexity at large

The following news item is drawn in part from a news article in the 1 May 2003 edition of Nature titled “Complicity of Gene and Pseudogene” by Jeannie T. Lee. Science magazine dubbed RNA interference (RNAi) its “Breakthrough of the Year” in 2002. The RNAi discovery is that small RNA molecules, so small they had been classified as irrelevant trimmings, can regulate other RNA by base pairing with it and hence inactivating it. This means that the RNA that is trimmed from a genetic transcript before the rest of an RNA molecule is sent to the ribosomes to be transformed into protein might not just be trash. It might in fact play an important regulatory function. Pseudogenes are gene-like stretches of DNA that were noted decades ago and classified as genetic “fossils.” The reasoning held that pseudogenes were formerly useful genes that had been inactivated by mutation or some other DNA-transforming event but that had not yet finished degrading into totally junk DNA. Pseudogenes are transcribed into RNA, just like normal genes, but the RNA they produce does not make it to the ribosomes for translation into protein. With the discovery of RNAi, a new role for pseudogenes has become apparent. If RNAi is a regulatory mechanism, then stretches of DNA that generate apparently useless RNA might in actuality be generating regulatory signals. The discovery of RNAi reveals a whole new layer of genetic controls in a system whose complexity is already mindbending. Writing in Nature, Jeannie T. Lee summarizes findings that indicate the Makorin1-p1 pseudogene in humans has a regulatory function. While this regulatory function has not yet been conclusively demonstrated to be RNAi, the fact a pseudogene regulates the development of several organs shows that pseudogenes are more than genetic fossils. The finding that pseudogenes and genes appear in roughly equal numbers in humans is now less puzzling; instead of degrading into junk DNA over time, pseudogenes are conserved because they have a biological role to play. The discovery of new biological controls for the genome presages new techniques in fields as diverse as medicine and crop modification.