title: In vivo association of the stability control protein alphaCP with actively translating mRNAs.
abstract: Posttranscriptional controls play a major role in eucaryotic gene expression. These controls are mediated by sequence-specific interactions of cis-acting determinants in target mRNAs with one or more protein factors. The positioning of a subset of these mRNA-protein (RNP) complexes within the 3' untranslated region (3' UTR) may allow them to remain associated with the mRNA during active translation. Robust expression of human alpha-globin mRNA during erythroid differentiation has been linked to formation of a binary complex between a KH-domain protein, alphaCP, and a 3' UTR C-rich motif. Detection of this "alpha-complex" has been limited to in vitro studies, and the functional state of the alpha-globin mRNA targeted by alphaCP has not been defined. In the present study we demonstrate that a significant fraction of alphaCP is associated with polysomal mRNA. Targeted analysis of the polysomal RNP complexes revealed that alphaCP is specifically bound to actively translating alpha-globin mRNA. The bound alphaCP is restricted to the poly(C)-rich 3' UTR motif and is dislodged when ribosomes are allowed to enter this region. These data validate the general importance of the 3' UTR as a sheltered site for RNP complexes and support a specific model in which the stabilizing function of alphaCP is mediated on actively translating target mRNAs.
authors.affiliation: Department of Genetics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, USA.
authors.forename: Xinjun
authors.initials: X
authors.lastname: Ji
authors.forename: Jian
authors.initials: J
authors.lastname: Kong
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Liebhaber
mesh_terms: D020413:3' Untranslated Regions; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D004268:DNA-Binding Proteins; D005914:Globins / Q000235:genetics; D006801:Humans; D051379:Mice; D008954:Models, Biological; D011132:Polyribosomes / Q000378:metabolism; D014176:Protein Biosynthesis; D012323:RNA Processing, Post-Transcriptional; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism*; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins / Q000235:genetics / Q000378:metabolism
chemical_list: D020413:3' Untranslated Regions; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C121375:Pcbp1 protein, mouse; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D012261:Ribonucleoproteins; D005914:Globins