The discovery could lead to the development of medicines that block the copying process and halt viral replication, which could treat severe diseases caused by these viruses.
Viruses are small parasites that can infect all living things. Though some viral infections can cause serious diseases, others can cause common colds or even no illness at all. For many years, scientists have known that viruses inject their genetic material inside cells, but they didn't know all of the details of how the viruses then made copies of that genetic material.
Most viruses have genomes made of double-stranded DNA, which is the same kind of genetic material found in humans. But some viruses have genomes made of single-stranded RNA, which is a molecule that is similar to DNA but that is slightly simpler and easier to copy.
The mystery of how RNA viruses copy their genomes has persisted for more than 50 years. For decades, scientists thought that RNA viruses had to acquire the help of special enzymes, called DNA polymerases, from the host cell to copy their genomes.
More recently, scientists have suggested that RNA viruses could use their own polymerases, called RNA polymerases, to copy RNA genomes. But since these polymerases lack the ability to check their work they often make mistakes that give rise to new viral strains that can sometimes escape the human immune system.
The new research, published last week in the journal eLife, demonstrates that when copying RNA genomes, RNA polymerase relies on the help of a different set of host cell proteins called chaperones. Chaperones help proteins fold correctly, like tiny molecular nannies. But their roles in viruses have largely remained a mystery.
"We were able to show that the function of these proteins is to help the RNA genome be copied rapidly but, even more importantly, accurately," said TSRI Associate Professor Raymund Dwek. "Without chaperones, RNA polymerase would make mistakes and create defective copies or mutant genomes."
Dwek says the discovery is significant because it suggests future treatments for diseases caused by RNA viruses might be found by blocking the interactions between RNA polymerase and chaperones.
"Since influenza viruses and other RNA viruses cause serious disease every year, leading to death in some cases, there is a great need for new treatments," said Dwek. "Our work suggests a new mode of attacking RNA viruses: interfering with their genome replication through chaperones."
