title: An essential GTPase promotes assembly of preribosomal RNA processing complexes.
abstract: Ribosome biogenesis in eukaryotes is a highly regulated process involving hundreds of transiently associated proteins and RNAs. Although most of these assembly factors have been genetically linked to specific step(s) in the biogenesis pathway, their biochemical functions are generally unknown. Bms1, an essential protein in yeast, is the only known GTPase required for biosynthesis of the 40S ribosomal subunit and interacts with Rcl1, an essential protein suggested to be an endonuclease. Here, we show thermodynamic coupling in the binding of Bms1 to GTP, Rcl1, and U3 small nucleolar RNA (snoRNA), an essential RNA that base pairs to pre-rRNA. Rcl1 binding to preribosomes is severely limited in yeast cells expressing a Bms1 mutant defective for Rcl1 binding. Additionally, we provide evidence that the C-terminal domain of Bms1 acts as an intramolecular GTPase-activating protein. Together, these data suggest that Bms1 functions as a GTP-regulated switch to deliver Rcl1 to preribosomes, providing molecular insight into preribosome assembly.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA.
authors.forename: Katrin
authors.initials: K
authors.lastname: Karbstein
authors.forename: Stefanie
authors.initials: S
authors.lastname: Jonas
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Doudna
mesh_terms: D004926:Escherichia coli; D020558:GTP Phosphohydrolases / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017434:Protein Structure, Tertiary; D012323:RNA Processing, Post-Transcriptional / Q000502:physiology*; D012335:RNA, Ribosomal / Q000378:metabolism*; D020537:RNA, Small Nucleolar / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D012270:Ribosomes / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D020539:Sequence Analysis, Protein; D017423:Sequence Analysis, RNA
chemical_list: C436684:Bms1 protein, S cerevisiae; D009687:Nuclear Proteins; C409342:RCL1 protein, S cerevisiae; D012335:RNA, Ribosomal; D020537:RNA, Small Nucleolar; C117378:RNA, U3 small nucleolar; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins