Ribosomal protein L14 contributes to the early assembly of 60S ribosomal subunits in Saccharomyces cerevisiae

Abstract

The contribution of most ribosomal proteins to ribo- some synthesis has been quite well analysed in Sac- charomyces cerevisiae . However, few yeast riboso- mal proteins still await characterization. Herein, we show that L14, an essential 60S ribosomal protein, assembles in the nucleolus at an early stage into pre- 60S particles. Depletion of L14 results in a deficit in 60S subunits and defective processing of 27SA 2 and 27SA 3 to 27SB pre-rRNAs. As a result, 27S pre-rRNAs are subjected to turnover and export of pre-60S par- ticles is blocked. These phenotypes likely appear as the direct consequence of the reduced pre-60S par- ticle association not only of L14 upon its depletion but also of a set of neighboring ribosomal proteins located at the solvent interface of 60S subunits and the adjacent region surrounding the polypeptide exit tunnel. These pre-60S intermediates also lack some essential trans -acting factors required for 27SB pre- rRNA processing but accumulate practically all fac- tors required for processing of 27SA 3 pre-rRNA. We have also analysed the functional interaction be- tween the eukaryote-specific carboxy-terminal exten- sions of the neighboring L14 and L16 proteins. Our results indicate that removal of the most distal parts of these extensions cause slight translation alter- ations in mature 60S subunits.