RNA et biosynthèse de l'hémoglobine.

Abstract

In 1960, we have observed with G. Schapira and J. C. Dreyfus that when ribosomes from rabbit reticulocytes were incubated with the pH 5 fraction from guinea pig reticulocyte, as well as in the reverse system, both rabbit and guinea pig hemoglobins were synthesized. The discovery of the messenger RNA by Jacob and Monod allowed us to give an explanation of these observations. The reality of these synthesis was ascertained by the method of double labelling and peptide analysis. In order to demonstrate the presence of messenger RNA in reticulocytes we have purified RNA from these cells. Hemoglobin synthesis was stimulated when this RNA was added to a reticulocyte cell free system. This RNA was fractionated on a sucrose gradient. The fraction which sedimented between 18S and 4S, and which was called RNA III, stimulated hemoglobin cell free synthesis. The stimulation is specific, since: u – The other RNA fractions did not stimulate hemoglobin synthesis. – RNA III from reticulocytes from other species were either inactive or inhibitory. These results are in favor of the presence of messenger RNA in this fraction in reticulocytes. RNAs extracted from rabbit, liver, kidney, intestine nuclei, and the fraction III from these RNAs also stimulated hemoglobin synthesis. RNA from cytoplasm, RNA III from liver nuclei from other species did not stimulate hemoglobin synthesis. These results favor the idea that nuclei from differentiated cells contain messenger RNAs which are not translated in these cells. We are now studying mechanims involved in the selection of messenger RNAs in differentiated cells.