Hierarchical recruitment into nascent ribosomes of assembly factors required for 27SB pre-rRNA processing in Saccharomyces cerevisiae.
To better define the roles of assembly factors required for eukaryotic ribosome biogenesis, we have focused on one specific step in maturation of yeast 60 S ribosomal subunits: processing of 27SB pre-ribosomal RNA. At least 14 assembly factors, the 'B-factor' proteins, are required for this step. These include most of the major functional classes of assembly factors: RNA-binding proteins, scaffolding protein, DEAD-box ATPases and GTPases. We have investigated the mechanisms by which these factors associate with assembling ribosomes. Our data establish a recruitment model in which assembly of the B-factors into nascent ribosomes ultimately leads to the recruitment of the GTPase Nog2. A more detailed analysis suggests that this occurs in a hierarchical manner via two largely independent recruiting pathways that converge on Nog2. Understanding recruitment has allowed us to better determine the order of association of all assembly factors functioning in one step of ribosome assembly. Furthermore, we have identified a novel subcomplex composed of the B-factors Nop2 and Nip7. Finally, we identified a means by which this step in ribosome biogenesis is regulated in concert with cell growth via the TOR protein kinase pathway. Inhibition of TOR kinase decreases association of Rpf2, Spb4, Nog1 and Nog2 with pre-ribosomes.
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Jason
J
Talkish
Jingyu
J
Zhang
Jelena
J
Jakovljevic
Edward W
EW
Horsey
John L
JL
Woolford
D053487:DEAD-box RNA Helicases / Q000378:metabolism; D020558:GTP Phosphohydrolases; D008780:Methyltransferases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism
C107936:NIP7 protein, S cerevisiae; C514434:Nsa2 protein, S cerevisiae; D009687:Nuclear Proteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; C451023:RPF2 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C491609:TIF6 protein, S cerevisiae; D008780:Methyltransferases; C091276:NOP2 protein, S cerevisiae; D058570:TOR Serine-Threonine Kinases; C411109:DBP10 protein, S cerevisiae; D020558:GTP Phosphohydrolases; C477781:NOG2 protein, S cerevisiae; C063215:SPB4 protein, S cerevisiae; D053487:DEAD-box RNA Helicases