Northern blot analysis of induction of β-globin gene expression in the parental MEL-B8/3 cells and transfectants cultured under various conditions. Total RNA was extracted from the cells cultured for 72 hours in the ordinary medium or in the medium containing 1.5% DMSO alone or 1.5% DMSO and 100 μmol/L ZnCl₂ and was hybridized with ²³P-labeled probes.