Globin messenger-RNA induction during erythroid differentiation of cultured leukemia cells

A cloned line of murine proerythroblastoid cells (T-3-Cl-2), transformed by Friend leukemia virus, undergoes changes associated with erythroid differentiation when treated with dimethylsulfoxide in culture. This line, which does not undergo spontaneous differentiation, develops specific erythrocyte-membrane antigen and accumulates detectable amounts of heme within four days of dimethylsulfoxide treatment. In the present study, we have followed the phenotypic expression of the globin genes by measuring globin mRNA in differentiating cells. Our hybridization probe for this purpose is [(3)H]DNA, which is complementary to purified globin mRNA, synthesized by viral RNA-directed DNA polymerase. This probe is sufficiently sensitive to detect less than 1 ng of globin mRNA. Using it, we find little or no hybridizable globin mRNA in either uninduced cells or in treated control lymphoid cells. In contrast, globin mRNA can be detected in T-3-Cl-2 cell 2 days after induction by dimethylsulfoxide; it reaches a maximum concentration four days after induction. At this time, cells that stain positively for heme appear. The hybridizable cytoplasmic RNA induced in these cells has the sedimentation properties of 9S globin mRNA. Considering the stable character of globin mRNA, our results are most readily explained in terms of a transcriptional activation of the globin genes.