Ribosomal proteins L7 and L8 function in concert with six A₃ assembly factors to propagate assembly of domains I and II of 25S rRNA in yeast 60S ribosomal subunits.
Ribosome biogenesis is a complex multistep process that involves alternating steps of folding and processing of pre-rRNAs in concert with assembly of ribosomal proteins. Recently, there has been increased interest in the roles of ribosomal proteins in eukaryotic ribosome biogenesis in vivo, focusing primarily on their function in pre-rRNA processing. However, much less is known about participation of ribosomal proteins in the formation and rearrangement of preribosomal particles as they mature to functional subunits. We have studied ribosomal proteins L7 and L8, which are required for the same early steps in pre-rRNA processing during assembly of 60S subunits but are located in different domains within ribosomes. Depletion of either leads to defects in processing of 27SA(3) to 27SB pre-rRNA and turnover of pre-rRNAs destined for large ribosomal subunits. A specific subset of proteins is diminished from these residual assembly intermediates: six assembly factors required for processing of 27SA(3) pre-rRNA and four ribosomal proteins bound to domain I of 25S and 5.8S rRNAs surrounding the polypeptide exit tunnel. In addition, specific sets of ribosomal proteins are affected in each mutant: In the absence of L7, proteins bound to domain II, L6, L14, L20, and L33 are greatly diminished, while proteins L13, L15, and L36 that bind to domain I are affected in the absence of L8. Thus, L7 and L8 might establish RNP structures within assembling ribosomes necessary for the stable association and function of the A(3) assembly factors and for proper assembly of the neighborhoods containing domains I and II.
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Jelena
J
Jakovljevic
Uli
U
Ohmayer
Michael
M
Gamalinda
Jason
J
Talkish
Lisa
L
Alexander
Jan
J
Linnemann
Philipp
P
Milkereit
John L
JL
Woolford
D021581:Active Transport, Cell Nucleus / Q000235:genetics / Q000502:physiology; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D046228:Microarray Analysis; D030781:Organisms, Genetically Modified; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology; D012322:RNA Precursors / Q000378:metabolism; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics / Q000502:physiology; D012335:RNA, Ribosomal / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
D012322:RNA Precursors; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; C053634:RPL7 protein, human; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C075184:ribosomal protein L8, rat; C065039:RNA, ribosomal, 25S