Not4 and Not5 Modulate Translation Elongation Dynamics Via Rli1 and Rps7a Ubiquitination, and Condensates that Exclude eIF5A

Abstract

In this work we determine that Not4 and Not5 of the Ccr4-Not complex modulate translation elongation dynamics and change A-site ribosome dwelling in a codon-dependent fashion. These codon-specific changes in cells lacking Not5 are very robust, independent of codon position within the mRNA, the overall mRNA codon composition, expression levels or changes of mRNA levels in the absence of Not5, but inversely correlate with those in cells depleted for eIF5A and positively with those in cells depleted for ribosome-recycling factor Rli1. Not4 ubiquitinates Rli1, but overexpressed Rli1 that fails to get ubiquitinated induces read through at poly-Arg stretches, which also occurs in absence of Rps7A ubiquitination. Not5 shows punctate cytoplasmic staining, co-purifies with ribosomes and Rli1, but not eIF5A and limits mRNA solubility. We propose that Not4 and Not5 set translation elongation dynamics to produce a soluble proteome via Rli1 and Rps7A ubiquitination, and condensates excluding eIF5A.