Expression of the AML-1 oncogene shortens the G(1) phase of the cell cycle

AML-l-encoded transcription factor, AML-1B, regulates numerous hematopoieti c-specific genes. Inappropriate expression of AML-1-family proteins is onco genic in cell culture systems and in mice. To understand the oncogenic func tions of AML-1, we established cell lines expressing AML-1B to examine the role of AML-1 in the cell cycle. DNA content analysis and bromodeoxyuridine pulse-chase studies indicated that entry into the S phase of the cell cycl e was accelerated by up to 4 h in AML-1B-expressing 32D.3 myeloid progenito r cells as compared with control cells or cells expressing E2F-1. However, AML-1B was not able to induce continued cell cycle progression in the absen ce of growth factors. The DNA binding and transactivation domains of AML-1B were required for altering the cell cycle. Thus, AML-1B is the first trans cription factor that affects the timing of the mammalian cell cycle.