Efficient translation and polyribosome binding of ¹²⁵I‐labelled rabbit globin messenger ribonucleoprotein

Rabbit polyribosomal globin messenger ribonucleoprotein (mRNP) was labelled under mild conditions, using 125I and Iodogen, in the protein moiety so that the fate of mRNA-associated proteins could be followed during translation. 125I-mRNP was shown to retain functional activity in the nuclease-treated reticulocyte lysate translation system under optimal labelling conditions. Polyribsome binding of 125I-mRNP and its sensitivity to cycloheximide indicated a functional- and translation-dependent binding of mRNP proteins. The results constitute a successful and direct approach to the study of mRNA-associated proteins in translational control.