Characterizaton of the chromatin remodelling activity of the transcription factor c-Myb

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The transcription factor c-Myb plays a key role in the control of proliferation, differentiation and apoptosis of hematopoietic cells and has been implicated in the development of leukemia and of certain non-hematopoietic tumors, such as breast and colon cancer. Although a number of Myb-regulated genes are known and several proteins interacting and cooperating with Myb have been identified, we have presently only a rather incomplete picture of how Myb stimulates the expression of its target genes in their native, chromatin-embedded state. Such a picture would significantly improve our understanding of the role of Myb in hematopoietic cells and would aid in the development of small molecule inhibitors of Myb. The overall goal of this project is to understand the molecular interactions between Myb and the transcriptional machinery that are relevant for the transcriptional regulation of Myb target genes in their native, chromatinized state. In our preliminary work we have studied the impact of Myb on the chromatin structure of the chicken mim-1 gene, a well-characterized Myb target gene, and identified a highly conserved region within the Myb transactivation domain, that plays a crucial role in chromatin remodelling by Myb. Our work shows that this region, referred to as chromatin remodelling domain (CRD), participates in protein-protein interactions with Myb itself as well as with several chromatin remodelling proteins, including the protein arginine methyl-transferase PRMT4, the histone acetyl-transferase TIP60 and Menin, an adaptor protein Mixed lineage leukemia (MLL) histone methyl-transferase complexes. In this project we plan to explore in detail how this domain and its molecular interactions control the activity of Myb as a transcription factor. Specifically, we will characterize intramolecular interactions mediated by the CRD and other parts of Myb, employ proteomic approaches to identify novel interaction partners of the CRD, and investigate the functional relevance of the interaction of the CRD with Menin, TIP60 and PRMT4. Overall, we expect that this work will significantly advance our understanding of the function of Myb as a transcription factor. We also expect that the characterization of the molecular interactions of the CRD will, on the longer run, permit us to establish assay systems for the development of therapeutic inhibitors of Myb function.