Globin mRNA species induced in Friend MEL745-PC4 cells by various chemical inducers analyzed by RNase protection assays. Treatment of cells with chemical inducers, RNA preparation, and RNase protection assays are described in Materials and Methods. The concentrations of agents used (L for low and H for high) are as listed in Table 2. The abbreviations of the inducers used are given in the legend of Table 2. Each RNA sample (10 μg) was hybridized separately with a mixture of ɛ, βh1, and β^maj/min probes and with a mixture of ζ, -1/-2, and actin probes as in Fig 2.