title: Overexpression in COS cells of p50, the major core protein associated with mRNA, results in translation inhibition.
abstract: p50, the major core protein of messenger ribonucleoprotein particles (mRNPs) in the cytoplasm of somatic mammalian cells, has been characterized previously as a member of the Y-box binding transcription factor family of proteins (YB-protein) by both high structural homology and ability to bind specifically the Y-box sequence in double-stranded DNA. YB proteins are present in a whole range of cell types and some have been identified as germ-specific cytoplasmic proteins masking stored mRNA from translation. Western blot analysis of the distribution of p50 in subcellular fractions of COS-1 cells shows that p50 is a cytoplasmic protein quantitatively associated with mRNA, both in polyribosomes and in free mRNPs. The level of p50 in COS-1 cells determined by Western immunoblotting is 0.10% of total protein, which is nearly equimolar to that of ribosomes and is approximately 5-10-fold higher than the mRNA level. Transient transfection of COS-1 cells with a p50-expressing vector results in a dramatic inhibition of protein synthesis. A control transfection with a vector expressing a frameshift mutant of p50 does not cause translation inhibition. Therefore the increase in p50 protein level is responsible for the inhibitory effect in these cells.
authors.affiliation: Department of Biological Chemistry, School of Medicine, University of California, Davis, CA 95616, USA. edavydov@midway.uchicago.edu
authors.forename: E K
authors.initials: EK
authors.lastname: Davydova
authors.forename: V M
authors.initials: VM
authors.lastname: Evdokimova
authors.forename: L P
authors.initials: LP
authors.lastname: Ovchinnikov
authors.forename: J W
authors.initials: JW
authors.lastname: Hershey
mesh_terms: D000818:Animals; D019556:COS Cells; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D014176:Protein Biosynthesis; D012333:RNA, Messenger; D011817:Rabbits; D012261:Ribonucleoproteins / Q000235:genetics* / Q000378:metabolism
chemical_list: D012333:RNA, Messenger; D012261:Ribonucleoproteins; C026452:messenger ribonucleoprotein