FIG. 7.

PIM mutants of Hoxa9 exhibit the same ability as wild-type Hoxa9 to reestablish differentiation arrest CM3neo cells but differ from wild-type Hoxa9 in reestablishing differentiation arrest in CM1puro cells. CM3neo (A) or CM1puro (C) cells were infected with retrovirus expressing wild-type Hoxa9 or mutants of Hoxa9 in the PIM or HD. At 48 h after infection of CM3neo cells, estrogen was removed, and the number of live nonadherent cells in the cultures was quantitated over 10 days. Populations whose differentiation arrest was reestablished by Hoxa9 proteins were analyzed for the level of Hoxa9 protein expression by immunoblotting using anti-Hoxa9 sera (B). At 48 h after infection of CM1puro cells, cells were selected for retroviral gene expression by growth in G418, and the abundance of Hoxa9 proteins was quantitated using anti-Hoxa9 immunoblotting before estrogen was removed (D). Once estrogen was removed, the abundance of live nonadherent cells was quantitated over 26 days. The identity of the Hoxa9 protein encoded by retrovirus used to infect each population is designated adjacent to the growth profiles in both panels A and C and above each lane in immunoblots B and D.