Half-life and rate of synthesis of globin messenger ribonucleic acid. Determination of half-life of messenger ribonucleic acid and its relative synthetic rate in erythroid cells.

The specific radioactivity of mouse globin mRNA in blood reticulocytes was measured after injection of [(3)H]uridine into anaemic mice up to 60h before collection of reticulocytes. From these data, the decay of the acid-soluble nucleotide pool in the marrow and the relative marrow-cell composition it is possible to build models that allow the cell life-times and half-life of mRNA in the erythroid cells of the marrow to be calculated. Best fit of models to these data favour a model with either one or two cell divisions from the onset of mRNA synthesis. The single-cell-division model has cell times of 20, 13 and 7h respectively for the basophilic erythroblast, polychromatophilic erythroblast and reticulocyte. The two-cell-division model has cell times of 12, 12, 12 and 7h for the basophilic erythroblast 1 and 2, polychromatophilic erythroblast and reticulocyte respectively. Both models have an mRNA half-life of 17h and a constant rate of mRNA synthesis until enucleation at the reticulocyte stage, when synthesis stops. A declining rate of mRNA synthesis can be accommodated in a two-cell-division model, when synthesis halves at each cell division and cell times are essentially the same as above, but mRNA half-life is either 9h in the basophilic and polychromatophilic erythroblasts and 17h in the later cells, or 10h in the basophilic erythroblasts and polychromatophilic erythroblasts and 14.5h in later cells. In all cases it is clear that mRNA synthesis occurs over a time-period of only 30-36h and that mRNA cannot be pre-synthesized in precursor erythroid cells.