The role of queuosine modification for virulence in Shigella flexneri

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Queuosine (Q) is a hypermodified 7-deazaguanine base that is found at the Wobble position of selected tRNAs, and it equilibrates translational speed between the respective C- and U-ending Q-codons. Interestingly, earlier work indicates that Q modification is not restricted to tRNAs, but that mRNAs may also carry this modification. Specifically, it was suggested that the mRNA of a virulence factor in Shigella flexneri is Q-modified. S. flexneri is a pathogenic bacterium that causes shigellosis (dysentery, a severe form of diarrhea) in humans. Based on our expertise in queuosine modification of tRNAs in fission yeast, we here will investigate how this modification affects global transcription and translation in S. flexneri. Using the novel Q-RIP-Seq technology that we developed for the unbiased detection of Q-modified RNAs, we will interrogate the S. flexneri transcriptome for RNAs other than tRNAs that are Q-modified. Potential targets will be further investigated using mutational profiling and direct RNA sequencing, and the functional relevance of the modification will be determined using molecular biology and genetics. Furthermore, we will investigate how the absence of queuosine modification alters global transcription and translation in this bacterium. Altogether, we will thus obtain an integrated view of how Q modification affects translation in this bacterium, and we will determine how this controls virulence in Shigella flexneri.