title: A translation regulatory particle containing the Xenopus oocyte Y box protein mRNP3+4.
abstract: In oocytes, nontranslated maternal mRNAs are packaged by protein into messenger ribonucleoprotein particles (mRNPs) that are masked from translation by protein-RNA interactions. Proteins associated with such masked states of mRNAs are particularly abundant in amphibian oocytes. One of these mRNP proteins from Xenopus oocytes, mRNP3+4 (also called FRG Y2a/b or p54/p56), binds to diverse mRNAs independent of their sequence and is the germ line member of the evolutionarily conserved Y box protein multigene family. Xenopus oocytes contain soluble pools of mRNP3+4 6 S oligomers, probably dimers, and larger approximately 15 S particles containing mRNP3+4 and additional proteins. Here we report the purification of this larger form as an approximately 320-kDa particle that contains mRNP3+4 and nine additional polypeptides, including mRNA-binding polypeptides of 34 and 36 kDa and a doublet of 110/105 kDa that proved to be nucleolin. The particle has a protein kinase activity that phosphorylates its own mRNP3+4, nucleolin, and a 31-kDa polypeptide component and exhibits translational inhibition in both the wheat germ extract and rabbit reticulocyte lysate systems. The presence of mRNP3+4 and nucleolin in this large translation regulatory particle suggests that it participates in an early step of mRNP assembly and masking.
authors.affiliation: Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Michigan 48202, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Yurkova
authors.forename: M T
authors.initials: MT
authors.lastname: Murray
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005786:Gene Expression Regulation; D008970:Molecular Weight; D005810:Multigene Family; D009687:Nuclear Proteins / Q000302:isolation & purification / Q000378:metabolism; D009865:Oocytes / Q000502:physiology*; D010750:Phosphoproteins / Q000302:isolation & purification / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011817:Rabbits; D012156:Reticulocytes / Q000378:metabolism; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D029867:Xenopus Proteins; D014982:Xenopus laevis; D000097796:Nucleolin
chemical_list: D009687:Nuclear Proteins; D010750:Phosphoproteins; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D029867:Xenopus Proteins; D000097796:Nucleolin; C075593:YBX2 protein, Xenopus