Ribozymes are RNA molecules that are capable of catalyzing specific biological reactions. Their discovery showed that RNA can act both as genetic material, like DNA, but also as enzymes, giving them a far wider range of roles than first thought.
Ribozymes largely function within the ribosome, the large complex that mediates the synthesis of proteins, encoded by incoming mRNA molecules, which are derived directly from specific genes. This interlinking between the generation of proteins (transcription) and the synthesis of proteins (translation) is referred to as the central dogma. Ribozymes function at each stage of the central dogma, catalyzing a number of key reactions.
One of the key actions of ribozymes is the splicing of pre-mRNA. When our genes are transcribed into messenger RNA (mRNA), molecules that carry the information outside of the nucleus to the ribosomes, the product produced isn’t the finished article. It contains parts of the transcribed gene called introns, which do not have any role in producing proteins. This ‘pre-mRNA’ has to be cut up and these introns removed before the ribosomes can synthesise proteins. Ribozymes are key mediators of this process, generating the mature mRNA that can be read by ribosomes to produce proteins.
This ‘reading’ by ribosomes consists of the complex moving along the building blocks of the mRNA and fetching the amino acid, the basic component of proteins, that is required. These amino acids are recruited by tRNA molecules, which themselves can only be synthesised by reactions catalyzed by ribozymes.
One of the more interesting uses of ribozymes is in therapeutics. Treatments for HIV are being developed that take advantage of the fact that some ribozymes are great at cutting up genetic information. Since HIV, the virus that is responsible for causing AIDS, have a genome that uses RNA instead of DNA as its carrier of genetic information, ribozymes can be altered to cut up the HIV genome. Specifically, the treatment being produced by Gene Shears Pty Ltd is targeted against the packaging signal of new virus produced by infected cells. Removing this packaging signal means infected cells produce empty shells of viruses, curbing infection
‘Til next time…