Regulation of myeloblastin gene expression in PLB-985 and NB4 cells. (A) Northern blot showing downregulation of myeloblastin RNA in PLB-985 cells induced to differentiate with 1.25% DMSO. Cells were treated from 1 hour to 4 days with DMSO. Five micrograms of total cell RNA from each sample was separated on agarose/formaldehyde gel, transferred to a nylon membrane, and probed with a myeloblastin cDNA probe. Photograph of EtBr-stained 28S rRNA band is shown, verifying integrity and equal loading of RNA. (B) PLB-985 cells were treated with 9-cis-RA or the selective ligands for 1, 2, 3, 4, and 7 days. Lane C contains control normal cell RNA.