Activation of human β-globin genes from nonerythroid cells by fusion with murine erythroleukemia cells

A human β-globin gene derived from an established human lymphoblast cell line was introduced into murine erythroleukemia (MEL) cells by cell fusion. The globin genes in MEL cells are inducible by dimethyl sulfoxide (Me₂SO); induction leads to the accumulation of mouse globin mRNA and hemoglobin. Globin mRNA was not detected in the cytoplasm of the human lymphoblast cells, even at low levels, whether or not these cells were treated with Me₂SO. In cell hybrids that had retained the lymphoblast-derived β-globin gene, human β-globin mRNA was induced by Me₂SO. Poly(A)-containing 10S human β-globin mRNA was detected in the cytoplasm of the hybrid cells. Karyologic and isozymic analyses of a series of hybrids and subclones showed that human β-globin gene expression occurred only in hybrids that retained human chromosome 11. Analysis of one hybrid bearing a deletion of both the β-globin and lactate dehydrogenase A genes indicated that the β-globin gene is located on the short arm of human chromosome 11. No other human chromosomes are required for human β-globin gene expression in MEL cell hybrids. We conclude that the restricted expression of a globin gene in a human nonerythroid cell can be reversed. Furthermore, all components required for the transcription, processing, and transport to the cytoplasm of a human globin mRNA appear to be present in mouse erythroleukemia cells. Thus cell fusion wih MEL cells provides a way to isolate permanent cell lines with functioning human globin genes. The techniques should be useful for studying the biochemical basis for abnormal function of mutant globin genes, such as those present in individual with the thalassemia syndromes.