Annual Reviews Virology, 2023
A comprehensive review covering the structural and mechanistic basis of programmed -1 ribosomal frameshifting (-1PRF) in RNA viruses. Here we provide a summary of historical perspectives, highlight recent advances and discuss to what extent a general model for −1PRF remains a useful way of thinking.
A bacterial ribosome hibernation factor with evolutionary connections to eukaryotic protein synthesis
Virtually all organisms cope with stress and starvation by arresting their protein synthesis and converting their ribosomes into a state of dormancy. In this state, ribosomes associate with so-called “dormancy” or “hibernation” factors to shield vulnerable active centers from degradation, and thus preserve a pool of intact, functional ribosomes until conditions improve. Here we describe a new bacterial ribosome hibernation factor, Balon, present in up to 20% of all bacteria. It has homology to the aeRF1 family of proteins, providing a long-predicted evolutionary connection to eukaryotic protein synthesis. Our cryo-EM structures illustrate how Balon is delivered to the A-site by EF-Tu of both vacant and actively translating ribosomes. We describe several unique structural features that allow this protein to protect multiple active centres of the ribosome.
Structural and molecular basis for cardiovirus 2A protein as a viral gene expression switch
Nature Communications, 2021
Cardioviruses need the 2A protein to activate ribosomal frameshifting during infection. Here we present the crystal structure of 2A from EMCV, revealing a new RNA-binding fold. We then investigate how 2A binds to a structured RNA element in the viral genome that regulates frameshifting. Using optical tweezers, we demonstrate that 2A stabilises this RNA element, increasing the force required to unwind it - likely explaining its mechanism of action. Finally, using cryo-EM we characterise a direct interaction between 2A and ribosomal RNA.
Investigating molecular mechanisms of 2A-stimulated ribosomal pausing and frameshifting in Theilovirus
Nucleic Acids Research, 2021
The 2A protein TMEV acts as a switch to stimulate frameshifting during infection. Here, we present the X-ray crystal structure of TMEV 2A and define how it recognises the stimulatory RNA element. Through examination of PRF in TMEV-infected cells by ribosome profiling, we identify a series of 2A-induced ribosomal pauses and present evidence of ribosome queueing at frameshifting signal.