Isolation and characterization of Nmi, a novel partner of Myc proteins.

The Myc family of oncogenes is thought to play an important role in cell proliferation, differentiation, and neoplastic transformation. Although the structure and expression of Myc genes are well characterized, the function and biochemical properties of the Myc proteins are less well understood. Here, using a yeast genetic screen, we identified a novel gene, Nmi, that binds to N-myc and C-myc. It also interacts with other transcription factors in yeast. The carboxyl terminus of Nmi shows homology to an interferon-induced leucine zipper protein, IFP 35, whereas its amino terminus is homologous to a coiled-coil heptad repeat in the C. elegans protein, CEF59. Co-precipitation studies of Nmi with N-myc and C-myc confirmed the interaction in mammalian cells. Nmi mRNA is expressed at low levels in all fetal and adult human tissues tested, except brain. Among several cancer cell lines, high expression of Nmi was found in myeloid leukemias, which also express high levels of C-myc. Nmi gene is localized on human chromosome 22q13.3. Translocations of this region have been reported in some human leukemias.