title: Cpc2/RACK1 is a ribosome-associated protein that promotes efficient translation in Schizosaccharomyces pombe.
abstract: Cpc2/RACK1 is a highly conserved WD domain protein found in all eucaryotes. Cpc2/RACK1 functions on mammalian signal transduction pathways most notably as an adaptor protein for the betaII protein kinase C isozyme. In single cell eucaryotes, Cpc2/RACK1 regulates growth, differentiation, and entry into G0 stationary phase. The exact biochemical function of Cpc2/RACK1 is unknown. Here, we provide evidence that Cpc2 is associated with the ribosome. Using immunoaffinity purification, we isolated ribosomal proteins in association with Cpc2/RACK1. Polysome and ribosomal subunit analysis using velocity gradient centrifugation of cell lysates demonstrated that Cpc2 co-sediments with the 40 S ribosomal subunit and with polysomes. Conditions known to disrupt ribosome structure alter sedimentation of the ribosome and of Cpc2/RACK1 coordinately. Loss of cpc2 does not dramatically alter the rate of cellular protein synthesis but causes a decrease in the steady state level of numerous proteins, some of which regulate methionine metabolism. Whereas real time PCR analysis demonstrated that transcriptional mechanisms are responsible for down-regulation of some of these proteins, one protein, ribosomal protein L25, is probably regulated at the level of translation.
authors.affiliation: Morse Institute for Molecular Genetics, Department of Microbiology and Immunology, State University of New York Downstate Medical Center, Brookyln, New York 1120-2098, USA.
authors.forename: Boris
authors.initials: B
authors.lastname: Shor
authors.forename: Jimmy
authors.initials: J
authors.lastname: Calaycay
authors.forename: Julie
authors.initials: J
authors.lastname: Rushbrook
authors.forename: Maureen
authors.initials: M
authors.lastname: McLeod
mesh_terms: D000939:Epitopes / Q000276:immunology; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000502:physiology*; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012568:Schizosaccharomyces / Q000235:genetics*; D029702:Schizosaccharomyces pombe Proteins
chemical_list: D000939:Epitopes; D000075370:Receptors for Activated C Kinase; D011956:Receptors, Cell Surface; D029702:Schizosaccharomyces pombe Proteins; C000617313:cpc2 protein, S pombe