Asc1p, a WD40-domain containing adaptor protein, is required for the interaction of the RNA-binding protein Scp160p with polysomes.
Scp160p interacts in an mRNA-dependent manner with translating ribosomes via multiple RNA-binding heterogeneous nuclear ribonucleoprotein K-homology (KH) domains. In the present study, we show by protein-protein cross-linking that Scp160p is in close proximity to translation elongation factor 1A and the WD40 (Trp-Asp 40)-repeat containing protein Asc1p at ribosomes. Analysis of a truncation mutant revealed that the C-terminus of Scp160p is essential for ribosome binding and that Cys(1067) at the C-terminus of Scp160p is required to obtain these cross-links. The interaction of Scp160p with ribosomes depends on Asc1p. In fast-growing yeast cells, nearly all Asc1p is tightly bound to ribosomes, but it can also be present in a ribosome-free form depending on growth conditions. The functional homologue of Asc1p, mammalian RACK1 (receptor of activated C kinase), was previously characterized as an adaptor protein bridging activated signalling molecules with their substrates. Our results suggest that Scp160p connects specific mRNAs, ribosomes and a translation factor with an adaptor for signalling molecules. These interactions might regulate the translation activity of ribosomes programmed with specific mRNAs.
Baum
Sonja
S
Center of Molecular Biology at University of Heidelberg (ZMBH), Im Neuenheimer Feld 282, D-69120 Heidelberg, Germany.
Bittins
Margarethe
M
Frey
Steffen
S
Seedorf
Matthias
M
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay / Q000379:methods; D019204:GTP-Binding Proteins; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation / Q000502:physiology; D009687:Nuclear Proteins / Q000378:metabolism*; D020648:Peptide Elongation Factor 1 / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D011132:Polyribosomes / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000378:metabolism* / Q000502:physiology; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology
C111825:ASC1 protein, S cerevisiae; D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D003432:Cross-Linking Reagents; D008565:Membrane Proteins; D009687:Nuclear Proteins; D020648:Peptide Elongation Factor 1; D010455:Peptides; D016601:RNA-Binding Proteins; C097262:SCP160 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019204:GTP-Binding Proteins