The team are the first to observe at a single-molecule level how the genetic material (genome) that forms the core of a single-strand RNA virus particle packs itself into its outer shell of proteins. Lead researcher Professor Peter Stockley said their results overturn accepted thinking about the process and could open a chink in the armour of a wide range of viruses.
"If we can target this process, it could lead to a completely new class of anti-virals that would be less likely to create resistant viruses than existing drugs, which tend to target individual proteins," Professor Stockley said.
A number of important viruses like the common cold and polio have RNA (ribonucleic acid) instead of DNA as their genetic material. The observations reveal that the viruses' RNA initially has a much greater volume than the virus particles created after they are packed inside their protein shell.
"We realised that the RNA genome must have to be intricately folded to fit into the final container, just like when you pack to go on holiday and need to fold your clothes to fit into the space in your suitcase," said co-author Dr Roman Tuma from the University of Leeds' Faculty of Biological Sciences.
When the team added proteins to the viral RNA they saw an immediate collapse in its volume.
"It seems that viral RNAs have evolved a self-folding mechanism that makes closing the 'viral suitcase' very efficient. It's as though 'the suitcase and the clothes' work together to close the lid and protect the content," Dr Tuma said.
"The viral RNAs, and only the viral RNAs, can do this trick of folding up to fit as soon as they see the 'suitcase' coming. That's the important thing. If we can interfere in that process we've got a completely novel drug target in the lifecycle of viruses," Professor Stockley said.
"At the moment there are relatively few antiviral drugs and they tend to target enzymes that the virus encodes in its genome. The problem is that the drugs target one enzyme initially and, within the year, scientists are identifying strains that have become resistant. Individual proteins are extremely susceptible to this mutation. A fundamental process like the one we're looking at opens the possibility of targeting the collective behaviour of essential molecules, which could be much less susceptible to developing resistance," explained Professor Stockley.
The same phenomenon is seen in both bacterial and plant viruses. "While we have not proved it yet, I would put money on animal viruses showing the same mechanism too," Professor Stockley added.
The team used sophisticated instrumentation custom built at the University that allowed them to make the first ever single-molecule measurements of viral assembly. This allowed researchers to observe individual viral particles one at a time. "The specific collapse, which can only be seen in such assays, was totally unexpected and overturns the current thinking about assembly," Professor Stockley said.
The team also includes PhD student Alexander Borodavka, whose Wellcome Trust studentship funded the new research. They have recently secured a grant from the Biotechnology and Biological Sciences Research Council (BBSRC) to extend their research.
"We're now perfectly positioned to pursue questions about how this mechanism works in other viruses and we're already thinking about ways to start designing new antiviral drugs that would target this newly recognised feature of viral lifecycles," Professor Stockley said.
The research is published in the Proceedings of the National Academy of Sciences (PNAS).
Graham Askew, Simon Walker, BBSRC (Jan 2018), £699,781
Jennifer Tomlinson, Royal Society (Jan 2018), £512,801
Jennifer Tomlinson, Royal Society-Research Fellows Enhancement Award (Dec 2017), £94,681
Helen Miller, AB AGri Grant (Dec 2017), £73,600
Simon Walker, Royal Society Enhancement Award (Dec 2017), £10,000
Carrie Ferguson, Bryan Taylor, Harry Rossiter, The Physiological Society (Dec 2017), £7,392
Ralf Richter, Royal Society (Dec 2017), £6,000
Christine Foyer, British Council Newton Fund (Dec 2017), £49,840
Adrian Whitehouse and colleagues in School of Chemistry and University of Liverpool, MRC (Nov 2017), £622,319
Michelle Peckham, Neil Ransom, MRC (Nov 2017), £495,159
Dave Lewis, British Council India (Nov 2017), £22,540
Elton Zeqiraj, Royal Society (Nov 2017), £15,000
Hannah Dugdale, Royal Society (Nov 2017), £15,000
Shaunna Burke, Cancer Research UK Innovation Grant (Nov 2017), £20,000
Alex O'Neill and colleagues in Chemistry, BBSRC (Nov 2017), £431,865
Jessica Kwok, Wings for Life (Nov 2017), £87,365
Tom Bennett, BBSRC (Oct 2017), £523,679
Neil Ranson, Darren Tomlinson, BBSRC (Oct 2017), £494,318
Nikita Gamper, BBSRC (Oct 2017), £490,426
Amanda Bretman and colleagues from UEA, NERC (Oct 2017), £430,886
Juan Fontana, Rosetrees Trust consumables grant (Oct 2017), £22,500
Helen Miller, DSM Nutritional Products AG (Sep 2017), £69,988
Neil Ranson, Juan Fontana, Mark Harris, Michelle Peckham, Ralf Richter, Peter Stockley, Patricija Van Oosten-Hawle and colleagues in Engineering, FMH and MAPS, Wellcome Trust Equipment Call (Sep 2017), £418,000
Jamie Johnston, Physiological Society (Sep 2017), £10,000
Frank Sobott, Adrian Goldman, Mark Harris, Andrew Macdonald, Stephen Muench, Sheena Radford and colleagues in FMH and MAPS, Wellcome Trust Equipment Call (Aug 2017), £415,000
Ralf Richter, David Brockwell, Eric Hewitt, Jessica Kwok, Emanuele Paci and MAPS/FMH, BBSRC (Jun 2017), £600,000
Eric Blair, Adrian Whitehouse, Nicola Stonehouse, Alison Baker, Richard Bayliss, Joan Boyes, Ryan Seipke, Sally Boxall and MAPS/FMH, BBSRC (Jun 2017), £376,000
Stefan Kepinski, Yoselin Benitez-Alfonso, Tom Bennett, Michelle Peckham, BBSRC (Jun 2017), £331,000
Roman Tuma, Lars Jeuken, Paul Millner, Sheena Radford, Peter Stockley and MAPS/FMH, BBSRC (Jun 2017), £222,000
Vas Ponnambalam, Darren Tomlinson, Stephen Wheatcroft, BHF (May 2017), £107,878
Graham Askew in collaboration with Bangor University, BBSRC (Mar 2017), £477,383
Stephen Muench, BBSRC (Mar 2017), £132,945
Nic Stonehouse, MRC (Mar 2017), £906,341
Bill Kunin, Steve Sait, BBSRC (Mar 2017), £602,831
Adrian Goldman, EU (Mar 2017), £546,576
Sheena Radford, Wellcome Trust (Mar 2017), £1,836,482
Beatrice Filippi, Royal Society (Mar 2017), £15,000
Tom Bennett, Royal Society (Mar 2017), £15,000
Jamie Johnston, Royal Society (Mar 2017), £15,000
Ryan Seipke, BBSRC (Feb 2017), £52,116
Mary O'Connell, BBSRC (Feb 2017), £46,986
Hannah Dugdale, NERC (Feb 2017), £504,138
Anastasia Zhuravleva, EPSRC (Jan 2017), £100,792