Cooperative and Mechanistic Roles of Mecom in Hematopoiesis

Thesis (Ph.D.)--University of Rochester. School of Medicine & Dentistry. Dept. of Pharmacology and Physiology, 2018.In this thesis, we sought to further understand the function of the Mecom gene, which encodes the transcription factors EVI1 and MDS1-EVI1 (PRDM3). Mecom is overexpressed in human leukemias, but its mechanism in oncogenesis is not well understood. We undertook an examination of three such possible mechanisms. First, we investigated protein interactions involving EVI1 in acute leukemia tissues. We identified a novel interaction between EVI1 and the SWI/SNF chromatin remodeling complex, verified co-localization at three EVI1 target genes, and narrowed down the physical site of interaction on EVI1. A second interest in the lab is the function of the PR domain, an N-terminal putative methyltransferase unique to the MDS1-EVI1 Mecom isoform. Preliminary data indicated that the domain is essential for leukemogenesis. We compared PRDM3’s structure to an active methyltransferase enzyme, identified residues that could be involved in enzymatic activity, and demonstrated that mutating these residues caused loss of PRDM3 function in a biological context. Lastly, we explored the hypothesis that PRDM3 and a closely related homolog, PRDM16, had redundant functions in vivo by generating a double knockout mouse model. Double knockout animals developed progressive pancytopenia due to HSC failure, a phenotype similar to Mecom inactivation in humans, revealing that PRDM3 and PRDM16 have additive effects on bone marrow maintenance. Overall, these studies provide critical information about Mecom’s function which we hope will lead towards future therapeutic strategies for human acute leukemias