Saccharomyces cerevisiae Ribosomal Protein L26 Is Not Essential for Ribosome Assembly and Function

Reyes Babiano,Jesús De La Cruz,John L Woolford,Michael Gamalinda

doi:10.1128/mcb.00539-12

Reyes Babiano, Jesús De La Cruz + Show 2 more

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https://doi.org/10.1128/mcb.00539-12

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Abstract

Ribosomal proteins play important roles in ribosome biogenesis and function. Here, we study the evolutionarily conserved L26 in Saccharomyces cerevisiae, which assembles into pre-60S ribosomal particles in the nucle(ol)us. Yeast L26 is one of the many ribosomal proteins encoded by two functional genes. We have disrupted both genes; surprisingly, the growth of the resulting rpl26 null mutant is apparently identical to that of the isogenic wild-type strain. The absence of L26 minimally alters 60S ribosomal subunit biogenesis. Polysome analysis revealed the appearance of half-mers. Analysis of pre-rRNA processing indicated that L26 is mainly required to optimize 27S pre-rRNA maturation, without which the release of pre-60S particles from the nucle(ol)us is partially impaired. Ribosomes lacking L26 exhibit differential reactivity to dimethylsulfate in domain I of 25S/5.8S rRNAs but apparently are able to support translation in vivo with wild-type accuracy. The bacterial homologue of yeast L26, L24, is a primary rRNA binding protein required for 50S ribosomal subunit assembly in vitro and in vivo. Our results underscore potential differences between prokaryotic and eukaryotic ribosome assembly. We discuss the reasons why yeast L26 plays such an apparently nonessential role in the cell.

Highlights

Ribosomal proteins play important roles in ribosome biogenesis and function
Pioneering work of Nomura and Nierhaus in the 1970s established that bacterial ribosomal subunits (r-subunits) could be reconstituted in vitro from mature ribosomal RNAs and r-proteins [40, 41, 65, 69, 70]
Ribosome synthesis proceeds via the formation of preribosomal intermediates that contain r-proteins and many nonribosomal proteins, so-called ribosome assembly or trans-acting factors, which likely provide this process with the necessary speed, accuracy, and directionality

Summary

Introduction

Ribosomal proteins play important roles in ribosome biogenesis and function. Here, we study the evolutionarily conserved L26 in Saccharomyces cerevisiae, which assembles into pre-60S ribosomal particles in the nucle(ol)us. The bacterial homologue of yeast L26, L24, is a primary rRNA binding protein required for 50S ribosomal subunit assembly in vitro and in vivo. Pioneering work of Nomura and Nierhaus in the 1970s established that bacterial ribosomal subunits (r-subunits) could be reconstituted in vitro from mature ribosomal RNAs (rRNAs) and r-proteins [40, 41, 65, 69, 70] These experiments demonstrated that r-subunits assemble in a cooperative and hierarchical manner through reconstitution intermediates (for reviews, see references 46 and 93). Insights into the approximate timing of association and dissociation of some of the protein ribosome biogenesis factors have been obtained by studying the composition of distinct pre-60S complexes purified from wild-type cells (reviewed in references 31 and 53) and from mutant strains blocked at early, intermediate, or late. The relative timing of the assembly of only a few 60S r-proteins has been investigated [4, 45, 84, 87, 90, 112]

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