June 18 (UPI) -- Members of a large groups of viruses, including influenza viruses, can build new genes using genetic code copied from hijacked human cells, according to new research.
When virologists surveyed the genetic diversity and protein synthesis capabilities of a group of viruses known as segmented negative-strand RNA viruses, or sNSVs, they found a variety of human pathogens can code for new proteins by combining host and viral sequences.
The so-called UFO proteins could explain why these viruses are so adept at infecting human hosts, but they could also be useful targets for future vaccines and anti-viral drugs.
Researchers detailed the production of these never-before-documented proteins in a new paper, published Thursday in the journal Cell.
"The capacity of a pathogen to overcome host barriers and establish infection is based on the expression of pathogen-derived proteins," study co-author Ivan Marazzi, professor of microbiology at the Icahn School of Medicine at Mount Sinai in New York, said in a news release. "To understand how a pathogen antagonizes the host and establishes infection, we need to have a clear understanding of what proteins a pathogen encodes, how they function, and the manner in which they contribute to virulence."
Viruses can't make their own proteins. To survive and replicate, they must find a host and hijack their cells. Once inside cells, they find ways to feed protein-making instructions to the host cell's protein-making machinery.
Viruses typically use "cap-snatching" to create protein-making codes, snipping off the end of one of the cell's messenger RNA sequences and combining it with a genetic sequence of their own.
"For decades we thought that by the time the body encounters the signal to start translating that message into protein (a 'start codon') it is reading a message provided to it solely by the virus," Marazzi said. "Our work shows that the host sequence is not silent."
The latest analysis showed that because sNSVs make mRNAs using their own genes, they're able to make protein-production instructions featuring host-derived start codons -- a technique called "start snatching." This ability allows sNSVs to synthesize previously unknown proteins using hybrid host-virus sequences.
Though previously invisible to scientists, these proteins are recognizable by the immune system, and they can alter the virulence of the invading virus, but more research is needed to determine the full functionality of UFO proteins.
"Viruses take over their host at the molecular level, and this work identifies a new way in which some viruses can wring every last bit of potential out of the molecular machinery they are exploiting," said study co-author Ed Hutchinson, research fellow at MRC-University of Glasgow Center for Virus Research. "While the work done here focuses on influenza viruses, it implies that a huge number of viral species can make previously unsuspected genes."
Researchers hope their research will illuminate new ways of attacking viruses with drugs and vaccines, and potentially aid the effort to thwart future pandemics and epidemics.