The stem-loop binding protein stimulates histone translation at an early step in the initiation pathway.
Metazoan replication-dependent histone mRNAs do not have a poly(A) tail but end instead in a conserved stem-loop structure. Efficient translation of these mRNAs is dependent on the stem-loop binding protein (SLBP). Here we explore the mechanism by which SLBP stimulates translation in vertebrate cells, using the tethered function assay and analyzing protein-protein interactions. We show for the first time that translational stimulation by SLBP increases during oocyte maturation and that SLBP stimulates translation at the level of initiation. We demonstrate that SLBP can interact directly with subunit h of eIF3 and with Paip1; however, neither of these interactions is sufficient to mediate its effects on translation. We find that Xenopus SLBP1 functions primarily at an early stage in the cap-dependent initiation pathway, targeting small ribosomal subunit recruitment. Analysis of IRES-driven translation in Xenopus oocytes suggests that SLBP activity requires eIF4E. We propose a model in which a novel factor contacts eIF4E bound to the 5' cap and SLBP bound to the 3' end simultaneously, mediating formation of an alternative end-to-end complex.
MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland, United Kingdom.
Barbara
B
Gorgoni
Stuart
S
Andrews
André
A
Schaller
Daniel
D
Schümperli
Nicola K
NK
Gray
Berndt
B
Müller
D020121:5' Untranslated Regions; D000818:Animals; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism; D005260:Female; D017930:Genes, Reporter; D006657:Histones / Q000235:genetics*; D006801:Humans; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008845:Microinjections; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism; D009866:Oogenesis; D010448:Peptide Initiation Factors / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000737:chemistry / Q000378:metabolism*; D016601:RNA-Binding Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013462:Sulfur Radioisotopes; D014981:Xenopus; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001616:beta-Galactosidase / Q000378:metabolism; D039221:mRNA Cleavage and Polyadenylation Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; D002352:Carrier Proteins; D039621:Eukaryotic Initiation Factor-3; D006657:Histones; D009687:Nuclear Proteins; C111580:PAIP1 protein, human; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C490491:SLBP1 protein, Xenopus; D013462:Sulfur Radioisotopes; D029867:Xenopus Proteins; D039221:mRNA Cleavage and Polyadenylation Factors; D008715:Methionine; D008156:Luciferases; D001616:beta-Galactosidase