RNA and Protein Metabolism in Normal Human Erythroblasts and Granuloblasts

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Abstract
Ribonucleic acid (RNA) and protein synthesis was studied in normal human myeloid cells by measuring autoradiographically tne uptake of tritiated nucleosides and leucine. The rate of RNA breakdown in these cells was studied by evaluating the release of the label after treatment with actinomycin. For every neolecule of leucine taken up into protein, immature myeloid cells synthesize a much greater amount of RNA than mature forms. It was also observed that in immature myeloid cells most of the RNA undergoes rapid breakdown. It is postulated that the RNA fraction with high turnover rate synthesized in immature granuloblasts and erythroblasts may be considered as a messenger fraction. Since an unstable RNA fraction is not evidenced in mature cells (metamyelocytes and orthochromatic erythroblasts) it seems possible that the information for protein synthesis is elaborated during the proliferative phase of the immature cells, so that any messenger RNA is attached to the ribosomes during the early stages of maturation.