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Tumorigenic N-terminal deletions of c-Myb modulate DNA binding, transactivation, and cooperativity with C/EBP
M Oelgeschläger1, E Kowenz-Leutz, S Schreek
1Institut für Molekularbiologie, Medizinische Hochschule Hannover, 30623 Hannover, Germany.
Abstract:
Oncogenic activation of c-myb by retroviral insertion has been implicated in tumor formation in chicken and mice. These genetic alterations result in deregulated expression of the c-myb gene and frequently in N-terminal truncation of the c-Myb protein. We demonstrate that truncation of the c-Myb N-terminus affects DNA binding and reporter activation. However, all three mutants, Myb Delta N20, Myb Delta N47 and Myb Delta N71 cooperated with C/EBP beta in reporter assays. In contrast to Myb Delta N20 and Myb Delta N47, however, the Myb Delta N71 mutant failed to activate the chromatin embedded endogenous mim-1 gene together with C/EBP beta. This suggests that an N-terminal region (amino acids 47-71) within repeat 1 (R1) of the murine c-Myb DNA binding domain affects activation of chromosomal target genes in collaboration with C/EBP beta.
Insights
Truncated c-Myb proteins, common in tumors, show altered DNA binding. A specific N-terminal region (amino acids 47-71) is crucial for activating target genes with C/EBP beta.
Area of Science:
- Oncogenes and Tumorigenesis
- Molecular Biology
- Gene Regulation
Background:
- Oncogenic activation of the c-myb gene via retroviral insertion is linked to tumor development in various species.
- Genetic alterations often lead to deregulated c-myb expression and N-terminal truncation of the c-Myb protein.
Purpose of the Study:
- To investigate the functional consequences of N-terminal truncation of the c-Myb protein on DNA binding and gene activation.
- To identify specific regions within the c-Myb N-terminus critical for activating chromosomal target genes in collaboration with C/EBP beta.
Main Methods:
- Generation and analysis of c-Myb N-terminal deletion mutants (Myb Delta N20, Myb Delta N47, Myb Delta N71).
- Reporter assays to assess DNA binding and transcriptional activation.
- Evaluation of activation of the endogenous mim-1 gene in collaboration with C/EBP beta.
Main Results:
- N-terminal truncation of c-Myb affects its DNA binding and reporter activation capabilities.
- Mutants Myb Delta N20, Myb Delta N47, and Myb Delta N71 all cooperated with C/EBP beta in reporter assays.
- The Myb Delta N71 mutant, unlike others, failed to activate the endogenous mim-1 gene with C/EBP beta, indicating a critical role for amino acids 47-71.
Conclusions:
- An N-terminal region (amino acids 47-71) within repeat 1 (R1) of the murine c-Myb DNA binding domain is essential for activating chromosomal target genes.
- This specific region is critical for the collaborative function of c-Myb and C/EBP beta in gene activation.
- Findings shed light on the mechanisms of c-Myb-mediated oncogenesis and gene regulation.