Open AccessThe Translational Repression of Globin mRNA in Free Cytoplasmic Ribonucleoprotein Complexes
Author(s) -
CIVELLI Olivier,
VINCENT Alain,
MAUNDRELL Kinsey,
BURI JacquesF.,
SCHERRER Klaus
Publication year - 1980
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1980.tb06066.x
Subject(s) - reticulocyte , globin , messenger rna , polysome , ribonucleoprotein , cytoplasm , microbiology and biotechnology , biology , protein biosynthesis , messenger rnp , p bodies , cell free system , biochemistry , chemistry , in vitro , ribosome , rna , translation (biology) , gene
The 20‐S globin mRNA‐protein complex isolated from the post‐polyribosomal supernatant of duck reticulocyte lysates was tested for its translational capacities in two different cell‐free protein‐synthesizing systems, one derived from wheat germ, the other derived from nuclease‐treated rabbit reticulocyte lysates. In both translational systems, the cytoplasmic free globin mRNA‐protein complex did not support protein synthesis whereas its fully deproteinized mRNA efficiently directed the synthesis of both the α and β globin polypeptide chains. Sedimentation of the 20‐S mRNA‐protein complex through exponential sucrose gradients containing 0.5 M KCl fractionated this complex into four different particles, from which two globin‐mRNA‐containing core particles were isolated. Neither of these globin‐mRNA‐containing core particles was translated in either the wheat germ or rabbit reticulocyte lysate system, whereas their extracted mRNA efficiently directed globin synthesis in vitro. These observations led to the conclusion that factors repressing translational activity are tightly bound to the free cytoplasmic globin mRNA in its ribonucleoprotein form; our data are also consistent with the notion that the associated translational repressing activity is, at least partly, mediated by protein. The results correlate in a functional manner, the different protein compositions observed in the active and inactive forms of globin mRNA‐protein complexes isolated respectively from the polyribosomal and the post‐polyribosomal cytoplasmic fractions of duck reticulocytes.