An isolated DNA of SEQ ID NO:1 is provided that encodes the transcription factor BP1, which is believed to be a repressor of the .beta.-globin gene. A host cell that is transformed with a vector that contains the DNA may be used to produce BP1. Vectors having a controllable promoter operably connected to the BP1 open reading frame may be used to transform .beta.-globin producing cells of patients with sickle cell anemia, thereby providing a treatment. Because BP1 is overexpressed in leukemia and breast cancer cells, acute myeloid leukemia, acute lymphocytic leukemia, and breast cancer can be screened for and diagnosed by determining whether BP1 is overexpressed in cell samples of patients who may have these conditions. An antisense DNA or RNA to the DNA encoding BP1 may be used as a treatment for acute myeloid leukemia, acute lymphocytic leukemia, and breast cancer.