Xrn1 biochemically associates to the eisosome after the post diauxic shift in yeast

Abstract

Gene expression is a crucial and well-orchestrated interplay between transcription, translation, and mRNAs and proteins decay. In eukaryotes, cytoplasmic mRNA decay is intimately linked to translation and mediated for a large part by the 5’- 3’ mRNA degradation pathway. After mRNA decapping by the DCP complex, with the assistance of its co-factors, the mRNA is degraded by the exonuclease Xrn1 (Parker 2012; Fromont-Racine and Saveanu 2014; for review). This enzyme is highly processive and requires a 5ʹ monophosphorylated RNA end, produced by decapping (Stevens 1988; Larimer and Stevens 1990). The coupling between mRNA degradation and translation is now well established. First, analyzes of yeast cellular extracts separated on sucrose gradient suggested that the 5’ mRNA degradation could occurs co-translationally (Hu et al. 2009). Second, mapping of the 5’-end by RNA-Seq revealed that degradation intermediates are phased according to a typical codon-specific trinucleotide shift pattern. This observation strongly indicated that at least a fraction of mRNAs degradation occurred during translation (Pelechano et al. 2015).Finally, a cryo-electron microscopy structure of yeast 80S ribosome–Xrn1 nuclease complex showed that Xrn1 can be intimately and specifically bound to the mRNA exit tunnel region of the ribosome, fully consistent with the fact that 5’- 3’ mRNA degradation pathway is physically coupled to translation (Tesina et al. 2019).