On the Mechanism of Erythropoietin-induced Differentiation: IX. INDUCED SYNTHESIS OF 9 S RIBONUCLEIC ACID AND OF HEMOGLOBIN

Abstract

Erythropoietin induces the synthesis of 9 S RNA and hemoglobin by cultured bone marrow cells derived from polycythemic rats and mice in which hemoglobin synthesis has been suppressed. Synthesis of 9 S RNA starts within 1 hour (rat cells) and 4 hours (mouse cells) of addition of erythropoietin to the medium, while hemoglobin synthesis is not initiated until 8 to 10 hours later. These findings indicate that there is another regulatory step between transcription, initiated by erythropoietin, and translation. Under conditions in which no hemoglobin synthesis occurs, bone marrow cells still synthesize a very small amount of 9 S RNA which may be a messenger for a protein other than globin. Comparison of stimulated hemoglobin synthesis by cells from normal animals with cells from polycythemic animals indicates that erythropoietin has an effect on some differentiated cells in the former population as well as on the undifferentiated cells in the latter population.