Characterization of the association of specific proteins with messenger ribonucleic acid

Abstract

Isolation of messenger ribonucleic acid (mRNA)-protein particles from cytosol or dissociated polyribosomes yielded complexes in which several proteins were consistently associated with mRNA. Some of the mRNA-associated proteins appeared to have a high affinity for mRNA since they remained complexed to mRNA during centrifugation in CsCl gradients. Quantitation of RNA and protein in polyribosomal mRNPs suggested that each molecule of mRNA bound a molecule of each of the two major proteins of 78 000 and 52 000 apparent molecular weights and/or one or more of several minor proteins found in mRNPs. Of the several mRNP proteins, only the protein of 78 000 apparent molecular weight appeared to form a stable complex with the polyriboadenylic acid [poly(A)]-tract of mRNA, suggesting that the remaining mRNA-associated proteins bind to other regions which may be common to many or all mRNAs. Binding of [3H]poly(A)-rich RNA to mRNP proteins was effectively inhibited by unlabeled poly(A)-rich RNA or the homopolymer polyriboguanylic acid [poly(G)], but not by poly(A) or other natural or synthetic mRNAs. The properties of non-poly(A)-dependent binding of mRNA by mRNP protein were similar to those of mRNA binding by the guanosine triphosphate dependent Met-tRNAfMet-binding protein.

Isolation and Characterization of Free Cytoplasmic Messenger Ribonucleoproteins from Rabbit Reticulocyte

“…Last, concerning rabbit reticulocyte free cytoplasmic messenger ribonucleoproteins, Barrieux et al [46] also found multiple bands on dodecylsulfate/ acrylamide gel (see also Results). On the contrary, Baglioni [Sl] found only two proteins, which are identical to the ones in polysomal messenger ribonucleoprotein.…”

“…One is to analyse the proteins bound to a mixture of different species of mRNA from a type of cell known to synthesize different kinds of proteins (e.g. Ehrlich ascites [46], HeLa [34]). In this case one may expect that the proteins common to most ribonucleoproteins would emerge, whereas proteins specific to individual mRNA would not be seen.…”

“…First, their number appear to be around 10-16 according to one-dimensional dodecylsulfate electrophoresis [18,34,46,47,49,50]. However, two-dimensional electrophoresis shows that free cytoplasmic messenger ribonucleoproteins contain many more proteins (see Results).…”

Identification in Xenopus laevis of a Class of Oocyte‐Specific Proteins Bound to Messenger RNA

“…Not only are there differences in the complexity of mRNP proteins [6, 311 but also in the protein:RNA ratio between the two classes. For instance, ratios of 0.5 and 4.0 were determined for mRNPs, washed with 0.5 M KC1, from polysomal and subribosomal fractions in ascites cells [16]. The properties of oocyte mRNP particles described here differ from those of polysomal mRNPs in several respects.…”

Inhibition of Protein Synthesis by Y Box-Binding Protein 1 Blocks Oncogenic Cell Transformation

“…As a DNAbinding protein, YB-1 binds to promoters containing the Y box element and either activates or represses gene expression (23,48,54,77). As an mRNA-binding protein, YB-1 is the most abundant protein of messenger ribonucleoprotein particles (mRNPs) and controls translation in a dose-dependent fashion (9,12,49). Low concentrations stimulate translation, and higher ones are inhibitory.…”