title: Characterization of hibernating ribosomes in mammalian cells.
abstract: Protein synthesis across kingdoms involves the assembly of 70S (prokaryotes) or 80S (eukaryotes) ribosomes on the mRNAs to be translated. 70S ribosomes are protected from degradation in bacteria during stationary growth or stress conditions by forming dimers that migrate in polysome profiles as 100S complexes. Formation of ribosome dimers in Escherichia coli is mediated by proteins, namely the ribosome modulation factor (RMF), which is induced in the stationary phase of cell growth. It is reported here a similar ribosomal complex of 110S in eukaryotic cells, which forms during nutrient starvation. The dynamic nature of the 110S ribosomal complex (mammalian equivalent of the bacterial 100S) was supported by the rapid conversion into polysomes upon nutrient-refeeding via a mechanism sensitive to inhibitors of translation initiation. Several experiments were used to show that the 110S complex is a dimer of nontranslating ribosomes. Cryo-electron microscopy visualization of the 110S complex revealed that two 80S ribosomes are connected by a flexible, albeit localized, interaction. We conclude that, similarly to bacteria, rat cells contain stress-induced ribosomal dimers. The identification of ribosomal dimers in rat cells will bring new insights in our thinking of the ribosome structure and its function during the cellular response to stress conditions.
authors.affiliation: Department of Nutrition, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
authors.forename: Dawid
authors.initials: D
authors.lastname: Krokowski
authors.forename: Francesca
authors.initials: F
authors.lastname: Gaccioli
authors.forename: Mithu
authors.initials: M
authors.lastname: Majumder
authors.forename: Michael R
authors.initials: MR
authors.lastname: Mullins
authors.forename: Celvie L
authors.initials: CL
authors.lastname: Yuan
authors.forename: Barbara
authors.initials: B
authors.lastname: Papadopoulou
authors.forename: William C
authors.initials: WC
authors.lastname: Merrick
authors.forename: Anton A
authors.initials: AA
authors.lastname: Komar
authors.forename: Derek
authors.initials: D
authors.lastname: Taylor
authors.forename: Maria
authors.initials: M
authors.lastname: Hatzoglou
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D006224:Cricetinae; D020285:Cryoelectron Microscopy; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism*; D006801:Humans; D051379:Mice; D014176:Protein Biosynthesis; D055503:Protein Multimerization; D051381:Rats; D012269:Ribosomal Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D013312:Stress, Physiological
chemical_list: D029968:Escherichia coli Proteins; D012269:Ribosomal Proteins; C063545:ribosome modulation factor, E coli