Isolation and characterization of murine erythroleukemia cell variants nonresponsive to hemin for the expression of globin genes

Thirty-four cloned lines of mouse erythroleukemia (MEL) cells that showed impairment in hemoglobin synthesis induced by hemin were isolated from line 745. Among these lines, 75% showed a reduced or nil response to induction by dimethyl sulfoxide (DMSO) and/or hypoxanthine. Four of these clones (three lines nonresponsive to hemin and one not responsive to either hemin or DMSO) were further characterized for the amount of globin mRNA accumulated in the cytoplasm and for the rate of globin synthesis upon exposure to hemin or DMSO. None of the four were induced by hemin to accumulate globin mRNA and all had a reduced rate of globin synthesis by comparison with control line 745. Two of the four lines had a high uninduced level of cytoplasmic globin mRNA not matched by a corresponding rate of globin synthesis, suggesting that they may accumulate defective globin mRNAs.