title: Function and ribosomal localization of aIF6, a translational regulator shared by archaea and eukarya.
abstract: The translation factor IF6 is shared by the Archaea and the Eukarya, but is not found in Bacteria. The properties of eukaryal IF6 (eIF6) have been extensively studied, but remain somewhat elusive. eIF6 behaves as a ribosome-anti-association factor and is involved in miRNA-mediated gene silencing; however, it also seems to participate in ribosome synthesis and export. Here we have determined the function and ribosomal localization of the archaeal (Sulfolobus solfataricus) IF6 homologue (aIF6). We find that aIF6 binds specifically to the 50S ribosomal subunits, hindering the formation of 70S ribosomes and strongly inhibiting translation. aIF6 is uniformly expressed along the cell cycle, but it is upregulated following both cold- and heat shock. The aIF6 ribosomal binding site lies in the middle of the 30-S interacting surface of the 50S subunit, including a number of critical RNA and protein determinants involved in subunit association. The data suggest that the IF6 protein evolved in the archaeal-eukaryal lineage to modulate translational efficiency under unfavourable environmental conditions, perhaps acquiring additional functions during eukaryotic evolution.
authors.affiliation: Dipartimento Biotecnologie Cellulari ed Ematologia, Policlinico Umberto I, Università di Roma Sapienza, Roma, Italy.
authors.forename: Dario
authors.initials: D
authors.lastname: Benelli
authors.forename: Stefano
authors.initials: S
authors.lastname: Marzi
authors.forename: Carmine
authors.initials: C
authors.lastname: Mancone
authors.forename: Tonino
authors.initials: T
authors.lastname: Alonzi
authors.forename: Anna
authors.initials: A
authors.lastname: la Teana
authors.forename: Paola
authors.initials: P
authors.lastname: Londei
mesh_terms: D019843:Archaeal Proteins / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D002453:Cell Cycle; D003001:Cloning, Molecular; D039642:Eukaryotic Initiation Factors / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D039662:Prokaryotic Initiation Factors / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D014176:Protein Biosynthesis; D012338:RNA, Ribosomal, 23S / Q000737:chemistry / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D054748:Ribosome Subunits, Large, Archaeal / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism; D048229:Sulfolobus solfataricus / Q000235:genetics* / Q000378:metabolism
chemical_list: D019843:Archaeal Proteins; D039642:Eukaryotic Initiation Factors; D039662:Prokaryotic Initiation Factors; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C041174:ribosomal protein L14