Biochemical characterization of MIP-1 alpha nuclear protein.

A family of hematopoietic specific transcription factors, MIP-1 alpha nuclear protein (MNP) family, has recently been identified. They are intimately involved in regulating the transcription of the huMIP-1 alpha gene in monocytes, T-cells, and transformed B-cells. One member of the family (MNP-1) is essential for promoter activity in monocytes and B-cells, while another (MNP-2) is required for full promotor activity in T-cells. A third member of the family (MNP-3) is expressed in PMA induced HL60 cells and probably has a role in monocyte differentiation. In this communication we demonstrate by two techniques that MNP-1 and MNP-2 are distinct but related factors, and we present further evidence to show that MNP-1 acts as a heterodimer.