This was a fantastic collaboration with the groups of @valerialulla.bsky.social @campathology.bsky.social and Trevor Sweeney @pirbrightinst.bsky.social. Thanks also to superb colleagues and facilities @biologyatyork.bsky.social, YSBL, @ybri-uoy.bsky.social and @diamondlightsource.bsky.social

These findings are similar to recent work on the EMCV Type 2 IRES — see e.g. www.biorxiv.org/content/10.1...; www.biorxiv.org/content/10.1... — and suggest that common structural motifs and mechanisms may exist within highly divergent picornavirus IRES sequences

To validate our structures, in collaboration with @valerialulla.bsky.social @campathology.bsky.social
, we carry out targeted disruption of domain IVc in related enterovirus CVA13. These mutations are highly detrimental to viral translation and replication in both HeLa and HIEC6 cell lines

IRES domain IVc contacts uS19 and uS13 on the 'head' of the small ribosomal subunit, whilst the conserved apical GNRA tetraloop interacts directly with the initiator tRNA

In our preprint, we reconstitute human translation initiation on a model poliovirus IRES and examine 48S complexes by cryo-EM. Our structures reveal a network of interaction between IRES domain IVc and the translation machinery during start-codon recognition (closed 48S complexes)

Enteroviruses use an internal ribosome entry site (IRES) within the 5′ UTR to recruit the translation machinery. Type 1 IRESs are large (~450 nt), flexible RNAs that require numerous eIFs and the host factor PCBP2 — making them very challenging structural targets

Thanks Dan :)

Thanks Ahmad, it was great to see you again too :)

Thanks also to the superb facilities at @biologyatyork.bsky.social, YSBL and @ybri-uoy.bsky.social, light source access @diamondlightsource.bsky.social and DESY, and to our funders, including @wellcometrust.bsky.social @royalsociety.org, BBSRC, EPSRC, DiMEN DTP and @thelisterinstitute.bsky.social

This was a fun collaboration with the brilliant
@steve-quinn-lab.bsky.social Mark Leake, @timcraggs.bsky.social, as well as Ian Brierley and @atomicvirology.bsky.social at @campathology.bsky.social

We explore the mechanism in detail, and make the argument that this represents a new class of protein-dependent riboswitch. It's perhaps useful to think about other frameshifting signals in a similar way - especially those with reported conformational plasticity.

Amazingly, this is not a stable structure. We use SAXS and single molecule FRET to show that the existence of this pseudoknot is entirely dependent on the 2A protein - without it, the RNA stays as a stem-loop, unable to activate frameshifting.

Here we present the structure of the 2A-RNA complex at 1.9 Å, revealing a novel RNA pseudoknot 👇

During virus genome translation, ribosomes encounter an unusual blockage: a complex between a structured RNA element and the mysterious viral 2A protein. This complex is essential to activate frameshifting, but how does it work?

Many RNA viruses use programmed -1 ribosomal frameshifting as an essential gene expression strategy. Cardioviruses (e.g. EMCV, TMEV) are the absolute masters of this, causing ~85 % of ribosomes to 'slip' into the -1 reading frame.

Thanks so much Dan, yes would be great to catch up soon😀