An evolutionarily conserved ribosomal protein Rps29/uS14 participates in the assembly of late pre-40S particles. In yeast Saccharomyces cerevisiae, duplicate genes RPS29A and RPS29B encode two paralogous proteins with 91% sequence identity. Here, we report that loss of either paralog impairs final step of cytoplasmic processing of 20S pre-rRNA, which is a direct precursor of mature 18S ribosomal RNA (rRNA)-a component of small ribosomal subunit. Consistently, we found that late processing factors remain bound to ribosome particles in Rps29-deficient cells. However, pre-40S particles containing 20S pre-rRNA are largely absent from translation-competent 80S ribosomes in Rps29-deficient cells, suggesting that lower levels of Rps29 protein induce quality control steps during maturation of cytoplasmic pre-ribosomal particles. Moreover, we analyzed Rps29 function during cellular stress conditions and found that cells with decreased levels of Rps29 protein adapted more rapidly to osmotic stress, but the effect was independent of the 20S pre-rRNA maturation.
Zadali et al. (Wed,) studied this question.