Unequal accumulation of α- and β-globin mRNA in erythropoietic mouse spleen

Relative amounts and rates of synthesis of α and β globin mRNAs were determined during splenic erythropoiesis in mice. At times after injection of mice with phenylhydrazine, α and β globin mRNAs were separated by gel electrophoresis and quantitated by densitometric scanning of stained gels. At 66 hr after injection, the ratio of β to α mRNA is about 1.2. By 138 hr, total globin mRNA is 5 fold greater in spleen cells, and the β to α mRNA ratio approaches 2. This ratio remains around 1 in reticulocytes throughout this period. Analyses of globin products directed by these mRNAs from spleen cells and reticulocytes in the ascites cell free system reflect the β to α mRNA ratio observed by electrophoresis. Relative rates of synthesis of globin mRNAs were estimated after incubation of spleen cells with either [³H]uridine or [³H]adenosine. Although synthesis of both mRNAs is maximal at 114 hr and then declines sharply, β mRNA is synthesized at a greater rate than α mRNA at every developmental stage. In contrast to the excess accumulation of β mRNA in spleen cells, synthesis of α and β globin chains remains balanced throughout erythroid development. These data suggest that during erythropoiesis in this system, equal synthesis of α and β globin involves regulation at both transcriptional and post transcriptional levels.