Interference with CBP and p300 function in erythroid cells leads to a block in differentiation.

MEL cells stably expressing a conditional, estradiol-dependent form of E1A were left untreated (U), or were treated with the differentiation-inducing agent DMSO (D), estradiol (E), or both (D/E). To monitor differentiation, cells were stained with benzidine, which stains hemoglobin (brown), and counterstained with May-Grunwald. Note the absence of benzidine-positive cells following estradiol-induced E1A activation (D/E). Control cell lines expressing mutant forms of E1A defective for CBP and p300 binding had no effect (not shown). For details, see Blobel et al.68