The initiation of globin synthesis in differentiating rabbit-bone-marrow erythroid cells.

At a particular stage of erythropoiesis, the immature erythroid cell commences synthesis of the messenger RNA for globin. Experiments were performed to determine whether this mRNA is immediately translated into globin or whether there is any substantial delay and accumulation of mRNA awaiting a further stage of differentiation. Rabbit bone marrow erythroid cells were separated according to their degree of maturity by velocity sedimentation on a sucrose gradient. Their relative abilities to synthesise globin were measured by radioactive labelling in culture and the relative proportions of globin mRNA in cellular RNA were determined by hybridisation to DNA complementary to globin mRNA. The increasing ability to synthesise globin closely parallelled the concentration of globin mRNA at all stages of differentiation, thus suggesting that there is no significant delay between transcription and translation.