Negative control of hemoglobin production in somatic cell hybrids due to heme deficiency

In somatic cell hybrids formed by the fusion of mouse erythroleukemic cells with mouse primary bone marrow cells, retention of the X chromosome contributed by the bone marrow parent is correlated with inhibition of hemoglobin accumulation in response to dimethyl sulfoxide. The inhibition of hemoglobin accumulation is not due to the absence of globin mRNA. Dimethyl sulfoxide-treated hybrid cells accumulate polyribosomal globin mRNA to levels comparable to those of the parental erythroleukemic cells under the same conditions. Heme, or its precursor δ-aminolevulinic acid, can overcome the effects of the bone marrow X chromosome and induce hemoglobin accumulation in the dimethyl sulfoxide-treated hybrid cells. The data suggest that the X chromosome contributed by the bone marrow cells inhibits hemoglobin production by inhibiting inducible heme biosynthesis, most probably at the step catalyzed by δ-aminolevulinic acid synthetase (EC 2.3.1.37).