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A new world of RNA medicines
Read more on - Polity | Economy | Schemes | S&T | Environment
- RNA, DNA, Proteins: The ribonucleic acid (RNA) is widely seen as a helpmeet molecule. It is said that production of RNA is the DNA’s main purpose; and production of proteins is RNA's main work. In 2021, however, vaccines made of RNA started giving protection against Covid-19 to millions of people around the world every day.
- A new revolution: Not only are RNA vaccines being considered for all sorts of other diseases, some of which have yielded to no other approach; other pharmaceutical uses of RNA look set to come into their own, as well.
- Links between DNA, RNA, Proteins: First came the discovery of DNA’s double-helix structure, and then an understanding of the way in which shapes and sequences were linked.
- The shape of a protein depends on the intricate way in which the chain of amino acids of which it consists is folded up.
- That depends in turn on the order in which amino acids of different types are strung together on that chain.
- And the order of the amino acids is a crucial part of the genetic information stored in the DNA sequences of the cell’s genome.
- The transfer of information from the genome to its active physical form in cell depends on RNA, a molecule in which both sequence and shape play crucial roles.
- The gene sequence is first copied from DNA to RNA, and that RNA transcript is then edited to form a molecule called a messenger RNA, or mRNA
- Ribosome: The end of the mRNA molecule is formatted into a distinctive shape which is recognised by ribosomes, complex pieces of machinery composed of dozens of proteins draped around another set of RNA molecules. With the help of yet more RNA molecules—little ones called tRNAs which stick to the mRNA sequence three letters at a time—the ribosome translates the genetic message into the protein it refers to by creating a chain of amino acids as it moves along the message.
- Vaccines for humans: This is the mechanism exploited by the RNA vaccines developed by BioNTech, a German biotechnology company, and Moderna, an American one from Massachusetts, against SARS-CoV-2, the virus which causes Covid-19. The companies mass produce the RN sequence describing the distinctive “spike” protein, which studs the outer membrane of the virus, formatted so as to look like a natural mRNA. These RNA molecules, wrapped in little fatty bubbles called liposomes are injected into patients, where the liposomes smuggle the mrna into cells. Ribosomes pick up on the mRNA format and read the sequence, thus producing the spike protein. The immune system learns to recognise the spike which the vaccinated cells are producing and stores away the memory of how to do so. This allows it to mount a swift response if it later comes across the same protein on the surfaces of viral particles and infected cells.
- A new era beings: This ability to get cells to churn out proteins for which their DNA contains no genes is, in itself, enough to open up a new world of medicine. But it is not the whole story. Cells make vast amounts of RNA that does not describe proteins. Its ability to recognise specific genetic sequences makes it useful for all sorts of processes, including turning the translation of genes on and off. Its ability to fold itself into particular forms—hairpins, loops and the like—makes it good at interacting with proteins. This alphabet soup of RNAs is a bit like a computer’s operating system, mediating the relationship between the cell’s hardware and its software.
- Many more diseases on target: Both the firms with mRNA vaccines on sale had other vaccines in the pipeline before Covid-19 struck. Now they are both getting on with what they had planned beforehand. Moderna is looking at vaccines to fend off infection by cytomegalovirus (a herpes virus which causes neurological problems in newborns), three lung viruses which cause respiratory disease in young children and Zika, a mosquito-borne virus found mainly in the tropics. BioNTech is focusing more on developing vaccines, and other treatments, with which to treat a wide range of cancers.
- Not just vaccines: Vaccination is not the only way that mRNA injection might fight viruses and tumours. The technique could also be used to get cells to produce therapeutic proteins that are currently administered through injection or infusion: interleukins and antibodies. Designer antibodies are a massive faff to make in industrial quantities; getting patients’ cells to take on the manufacturing duties instead would be a great step forward if it proved practical.
- A whole new approach: The application of RNA has met many obstacles over past decades, and the fact that it has proved itself in vaccines does not mean it will not meet more in the future. But it does seem that medicine now has a way to target drugs not just at proteins, but at the processes that make them, and that opens up new realms of possibility. The next RNA world awaits.
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