ABSTRACT
The earliest studies in this area focused on the highly abundant RNA species produced during terminal differentiation, which could be readily studied simply because of their abundance. Thus, even before the discovery of intervening sequences revealed the possibility of regulation at the level of RNA splicing, Gilmour et al. (1974) studied the processes regulating the accumulation of globin which occur when Friend erythroleukemia cells are treated with an inducer of globin production, dimethyl sulfoxide. In this system, the accumulation of cytoplasmic globin RNA, which produces the increase in synthesis of globin protein, was paralleled by increasing accumulation of globin RNA within the nucleus, suggesting that the primary effect of the inducer was at the level of globin gene transcription. Similarly, in the experiments of Groudine et al. (1974) globin-specific RNA was readily detectable in the nuclei of globin-synthesizing erythroblasts but not in the nuclear RNA of fibroblasts or muscle cells, hence indicating the involvement of transcriptional control in regulating the abundant production of globin RNA only in the red blood cell lineage and not in other cell types.
