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Isolation and characterization of Nmi, a novel partner of Myc proteins
1Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown Massachusetts 02129, USA.
Abstract:
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.
Insights
A novel gene, Nmi, was discovered to bind Myc proteins, crucial for cell growth and cancer. Nmi is highly expressed in myeloid leukemias, suggesting its role in cancer development.
Area of Science:
- Molecular Biology
- Oncology
- Genetics
Background:
- Myc oncogenes are vital for cell proliferation, differentiation, and cancer.
- The precise functions and biochemical properties of Myc proteins remain incompletely understood.
- Understanding Myc protein interactions is key to deciphering their role in neoplastic transformation.
Purpose of the Study:
- To identify novel proteins that interact with Myc family members, specifically N-myc and C-myc.
- To characterize the functional and structural properties of a newly identified Myc-interacting protein.
- To investigate the expression patterns of this novel protein in human tissues and cancer cell lines.
Main Methods:
- Yeast genetic screening to identify interacting partners of Myc proteins.
- Co-precipitation assays in mammalian cells to confirm protein-protein interactions.
- Quantitative analysis of Nmi mRNA expression in various human tissues and cancer cell lines.
- Gene mapping to determine the chromosomal location of the Nmi gene.
Main Results:
- A novel gene, Nmi, was identified through yeast screening for its ability to bind N-myc and C-myc.
- Nmi exhibits conserved domains, with its carboxyl terminus homologous to IFP 35 and its amino terminus to CEF59.
- Co-precipitation confirmed Nmi interaction with N-myc and C-myc in mammalian cells.
- Nmi mRNA is widely expressed but significantly elevated in myeloid leukemias, which also show high C-myc levels.
- The Nmi gene is mapped to human chromosome 22q13.3, a region implicated in some leukemias.
Conclusions:
- Nmi is a novel Myc-binding protein with potential roles in transcription regulation.
- The elevated expression of Nmi in myeloid leukemias suggests a role in the pathogenesis of these cancers.
- The chromosomal localization of Nmi to 22q13.3 may link it to chromosomal abnormalities observed in certain leukemias.