The effect of haemin on RNA synthesis and stability in differentiating rabbit erythroblasts

Abstract

Hemin accelerates the maturation of erythroid cells but whether this is the result of increased globin gene transcription or processing and stabilization of globin mRNA is not clear. The effect of hemin on the synthesis and stability of non-globin messengers is also unknown. The changes that occur in RNA metabolism were anemic rabbit bone marrow erythroblasts, fractionated into immature and mature fractions, are cultured with 20 .mu.M or 50 .mu.M hemin for brief periods (5-8 h) were examined. With both cell types hemin increases the incorporation of [3H]uridine into newly synthesized RNA, particularly into the poly(A)-rich fraction which can increase 3-fold. Hemin also increases the synthesis of globin mRNA (up to 500% absolutely and 50% relative to the synthesis of total RNA) in the immature, but not in the mature cells. Hemin probably increases the transcription of both globin and non-globin mRNA, and the relative increase of each depends on the stage of erythroid cell development. When the [3H]RNA from prelabeled cells was chased in the presence of hemin (with or without actinomycin D), the proportion of 3H remaining in globin mRNA increased in the immature, but not in the mature cells. These changes in the relative concentration of globin mRNA were also shown by the translation of extracted bone marrow RNA in a nuclease-treated reticulocyte lysate. A secondary effect of hemin is on RNA stability and it enhances the accumulation of globin mRNA by both molecular and cellular mechanisms.