A novel system to identify Myb target promoters in friend murine erythroleukemia cells.

Friend murine erythroleukemia (MEL) cells provide an early erythroid precursor model that can be induced to terminally differentiate in cell culture and has been used to study erythroid differentiation as well as multistage tumorigenesis. During the chemically induced differentiation of MEL cells, expression of the c-myb protooncogene is downregulated in a biphasic fashion and forced expression of c-myb is able to block the differentiation process, suggesting that c-myb activity may be limiting for differentiation in MEL cells. We have recently produced stable transfectants in the C19 MEL cell line that carry a dominant interfering myb allele (MEnT) under the control of an inducible mouse metallothionein I (MTH) promoter. Upon inducing expression of MEnT, transfected cells enter a differentiation program and begin to produce alpha-globin mRNA, assemble hemoglobin, and stop proliferating. Differential display was used to compare mRNA expression between parental C19 MEL cells induced to differentiate with hexamethylene bisacetamide (HMBA) and stable transfectants induced to differentiate via expression of MEnT to identify potential Myb target promoters. We identified six candidate cDNAs in this fashion and present evidence that two of these represent genes that are dependent on c-Myb activity for maximal expression in MEL cells.