Role of the yeast Rrp1 protein in the dynamics of pre-ribosome maturation.

Edward W Horsey,Tiffany D Miles,John L Woolford,Piyanun Harnpicharnchai,Jelena Jakovljevic

doi:10.1261/rna.5255804

Abstract

The Saccharomyces cerevisiae gene RRP1 encodes an essential, evolutionarily conserved protein necessary for biogenesis of 60S ribosomal subunits. Processing of 27S pre-ribosomal RNA to mature 25S rRNA is blocked and 60S subunits are deficient in the temperature-sensitive rrp1-1 mutant. We have used recent advances in proteomic analysis to examine in more detail the function of Rrp1p in ribosome biogenesis. We show that Rrp1p is a nucleolar protein associated with several distinct 66S pre-ribosomal particles. These pre-ribosomes contain ribosomal proteins plus at least 28 nonribosomal proteins necessary for production of 60S ribosomal subunits. Inactivation of Rrp1p inhibits processing of 27SA(3) to 27SB(S) pre-rRNA and of 27SB pre-rRNA to 7S plus 25.5S pre-rRNA. Thus, in the rrp1-1 mutant, 66S pre-ribosomal particles accumulate that contain 27SA(3) and 27SB(L) pre-ribosomal RNAs.

Highlights

Eukaryotic ribosome biogenesis is an evolutionarily conserved process that begins in the nucleolus with transcription of rRNA precursors and that ends in the cytoplasm with the formation of the mature 40S and 60S ribosomal subunits (Woolford and Warner 1991; Eichler and Craig 1994; Venema and Tollervey 1999; Olson 2000; Raue 2003; Tsochner and Hurt 2003)
The rrp1-1 mutation blocks two steps in pre-rRNA processing: conversion of 27SA3 pre-rRNA to 27SBS pre-rRNA, and cleavage of 27SB pre-rRNAs to generate 7S and 25.5S pre-rRNAs. In agreement with these pre-rRNA processing defects, we find that Rrp1p purifies with 66S pre-ribosomes containing 27SA2, 27SA3, 27SB, 25.5S, and 7S pre-rRNAs, as well as proteins necessary for biogenesis of 60S ribosomal subunits
The evolutionary conservation of functions required for ribosome biogenesis is reflected in the high degree of amino acid sequence homology of many ribosome synthesis factors among eukaryotes (Andersen et al 2002; Scherl et al 2002)

Summary

Introduction

Eukaryotic ribosome biogenesis is an evolutionarily conserved process that begins in the nucleolus with transcription of rRNA precursors and that ends in the cytoplasm with the formation of the mature 40S and 60S ribosomal subunits (Woolford and Warner 1991; Eichler and Craig 1994; Venema and Tollervey 1999; Olson 2000; Raue 2003; Tsochner and Hurt 2003). A subset of ribosomal proteins to form large ribosomal ribonucleoprotein particles (rRNPs), which are converted to mature ribosomal subunits (Warner and Soeiro 1967; Kumar and Warner 1972; Prestayko et al 1974; Trapman et al 1975; Trapman and Planta 1976; for review, see Hadjiolov 1985). These investigations established an ordered pathway of pre-ribosome formation. The 43S precursor particles are rapidly exported to the cytoplasm, where final steps of 40S subunit maturation occur, including production of mature 18S rRNA from 20S pre-rRNA (Udem and Warner 1973)

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Conclusion