Ribosomal Subunit Localization of Hemoglobin Messenger RNA

Abstract

When rabbit reticulocyte polyribosomes are treated with 0.5 M KCl, they dissociate into subunits and release a protein fraction which is required for peptide chain initiation in a cell-free system using KCl-treated subunits as the source of ribosomes. Three independent methods were used to determine the fate of mRNA after KCl treatment of the subunits. These three methods (sucrose gradient analysis of RNA after dissociating it from protein with sodium dodecylsulfate, acrylamide gel electrophoresis of RNA and electron microscopic analysis of subunits) all showed the 8--9-S mRNA to be associated with the small subunit, but not the large subunit. Furthermore, no mRNA was found to be associated with either "native" ribosomal subunit in a reticulocyte lysate.