Inability to rescue stalled ribosomes results in overactivation of the integrated stress response.

Endogenous and exogenous chemical agents are known to compromise the integrity of RNA and cause ribosome stalling and collisions. Recent studies have shown that collided ribosomes serve as sensors for multiple processes, including ribosome quality control (RQC) and the integrated stress response (ISR). Since RQC and the ISR have distinct downstream consequences, it is of great importance that organisms activate the appropriate process.

Host-Dependent Modifications of Packaged Alphavirus Genomic RNA Influence Virus Replication in Mammalian Cells.

Alphaviruses must interact efficiently with two distinct host environments in order to replicate and transmit between vertebrate and mosquito hosts. Some host-origin-dependent differences in virus particle composition that appear to facilitate the transmission cycle are known. However, the impact of host-mediated modification of packaged viral genomic RNA on subsequent infection has not been previously investigated.

N1-methylpseudouridine found within COVID-19 mRNA vaccines produces faithful protein products.

Synthetic mRNA technology is a promising avenue for treating and preventing disease. Key to the technology is the incorporation of modified nucleotides such as N1-methylpseudouridine (m1Ψ) to decrease immunogenicity of the RNA. However, relatively few studies have addressed the effects of modified nucleotides on the decoding process.

Ribosome quality control antagonizes the activation of the integrated stress response on colliding ribosomes.

Stalling during translation triggers ribosome quality control (RQC) to maintain proteostasis. Recently, stalling has also been linked to the activation of integrated stress response (ISR) by Gcn2. How the two processes are coordinated is unclear.

Oxidation and alkylation stresses activate ribosome-quality control.

Oxidation and alkylation of nucleobases are known to disrupt their base-pairing properties within RNA. It is, however, unclear whether organisms have evolved general mechanism(s) to deal with this damage. Here we show that the mRNA-surveillance pathway of no-go decay and the associated ribosome-quality control are activated in response to nucleobase alkylation and oxidation.

How do cells cope with RNA damage and its consequences?

Similar to many other biological molecules, RNA is vulnerable to chemical insults from endogenous and exogenous sources. Noxious agents such as reactive oxygen species or alkylating chemicals have the potential to profoundly affect the chemical properties and hence the function of RNA molecules in the cell. Given the central role of RNA in many fundamental biological processes, including translation and splicing, changes to its chemical composition can have a detrimental impact on cellular fitness, with some evidence suggesting that RNA damage has roles in diseases such as neurodegenerative disorders.

Ribosome Collisions Result in +1 Frameshifting in the Absence of No-Go Decay.

During translation, an mRNA is typically occupied by multiple ribosomes sparsely distributed across the coding sequence. This distribution, mediated by slow rates of initiation relative to elongation, ensures that they rarely collide with each other, but given the stochastic nature of protein synthesis, collision events do occur. Recent work from our lab suggested that collisions signal for mRNA degradation through no-go decay (NGD).

Ubiquitin-a beacon for all during quality control on the ribosome.

Ribosome stalling triggers no-go decay (NGD) and ribosome-associated quality control (RQC) pathways to rapidly degrade the aberrant mRNA and the incomplete nascent peptide, respectively. Two recent studies in yeast and mammalian systems reveal the importance of stalling-induced ribosomal protein ubiquitination by Hel2/ZNF598 for both NGD and RQC The studies also structurally explain how collided ribosomes generate a unique interface not present in monosomes, which can be recognized by Hel2/ZNF598 ubiquitin ligases.

Interactions between the mRNA and Rps3/uS3 at the entry tunnel of the ribosomal small subunit are important for no-go decay.

No-go Decay (NGD) is a process that has evolved to deal with stalled ribosomes resulting from structural blocks or aberrant mRNAs. The process is distinguished by an endonucleolytic cleavage prior to degradation of the transcript. While many of the details of the pathway have been described, the identity of the endonuclease remains unknown.

Ribosome Collision Is Critical for Quality Control during No-Go Decay.

No-go decay (NGD) is a eukaryotic quality control mechanism that evolved to cope with translational arrests. The process is characterized by an endonucleolytic cleavage near the stall sequence, but the mechanistic details are unclear. Our analysis of cleavage sites indicates that cleavage requires multiple ribosomes on the mRNA.