We have shown (manuscript submitted to Blood) that there is a correlation between the expression of the oncogenes c-myc and c-myb and the stage of development of cells of the erthroid lineage. Less mature cells make more oncogene transcript. Upon induction of differentiation by chemical agents, there is an abrupt fall (25 fold) in the level of both c-myb and c-myc transcript followed by a transient rebound. The levels of these messages tapers off until at the time of maximal globin production c-myb transcript is again 25 fold reduced while m-myc transcript is only 2-5 fold reduced compared to control culture. To test whether the alterations in oncogene transcript level is a necessary factor in the induction of differentiation, we are transfecting constitutive or regulatable constructs of these oncogenes into our murine erythroleukemia inducible cell lines. We hope to be able to control the level of oncogene message during the induction procedure and test the effect of varying transcript level on the progression of these cells toward terminal differentiation.