Abstract 3905: Structure–function relationships between RUNX1-MTG fusion proteins and core components of the Notch transcription complex

Abstract

Abstract The myeloid translocation genes (MTG) are preferred targets of chromosomal translocations with the Runx1 gene in acute myeloid leukemia (AML) pathogenesis. The resulting fusion proteins, RUNX1-MTG8 and RUNX1-MTG16, influence gene expression programs that control self-renewal and differentiation in hematopoiesis. How they engage the machinery of self-renewal to alter hematopoietic development is poorly understood. To gain additional insights into this question, we investigated structure–function relationships between RUNX1-MTG fusion proteins and core components of the Notch transcription complex, a critical determinant of cell fate specification in diverse tissues. The Notch transcription complex is composed minimally of the transcriptional repressor CSL, the intracellular domain of Notch receptors (N-ICD) and the transcriptional co-activator Mastermind (MAML). We show that RUNX1-MTG fusion proteins transactivate a Notch-responsive element from the Hes1 promoter. Using MTG16 as a model protein, we show that N-ICDs interact with a discrete domain in the MTG N-terminus. We translated these findings to the fusion proteins and found N-ICD binding was retained by RUNX1-MTGs and a RUNX1-MTG16 mutant that lacks the N1-ICD binding site. In parallel experiments, we defined the binding region for MTG proteins and their fusion protein derivatives on the N1-ICD. Informed by these structural relationships, we utilized RUNX1-MTG proteins or mutants that lack N1-ICD binding sites in transcriptional reporter assays. Our findings suggest that RUNX1-MTG fusion proteins alter transcription of the Notch target gene, Hes1 and intimate a structure–function relationship between RUNX1-MTG fusion proteins and Notch signaling. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3905.