Hematopoiesis, the process by which all blood cells are formed, is a complex and precisely regulated program. Differentiation and maturation of hematopoietic stem cells (HSCs) is controlled by several key factors, when perturbed hematopoiesis becomes dysregulated and leads to hematopoietic disorders and related malignancies. A master regulator of hematopoiesis, RUNX1, is a DNA binding transcriptional factor and contributes to HSC proliferation as well as differentiation. RUNX1 has been shown to control a broad, yet poorly defined transcriptional program, binding to other key hematopoietic factors such as PU.1 and working in cooperation with additional transcriptional regulators. Through protein-protein interaction studies, RUNX1 has been shown to bind co-activators such as p300 as well as co-repressors such as Sin3a. These discoveries add an additional later of complexity to RUNX1 transcription while DNA binding motif studies have yielded a core motif insufficient to describe RUNX1 binding. Currently, RUNX1 transcriptional mechanisms remain poorly understood with only isolated reports of RUNX1 targets in hematopoiesis. Recent have demonstrated that transcription factors regulate transcription through several mechanism beyond canonical DNA binding. Promoter-enhancer interactions in addition to contributions to DNA looping allow transcription factors to shape the 3D nucleome. In addition to RUNX1?s reported interaction with transcriptional regulators and new studies show control of hematopoietic enhancers such as Myb are mediated by RUNX1. Despite its critical role in hematopoiesis, the molecular mechanisms mediating RUNX1 transcription remain to be elucidated. Furthermore, RUNX1 has been linked to R-loop formation, RNA:DNA hybrids formed during transcription and linked to DNA damage. This places RUNX1 in a unique position, regulating transcription on a broad scale through both DNA binding and DNA looping while also contributing to underlying DNA damage related transcriptional processes. The proposal aims uncover the molecular mechanisms underlying RUNX1 transcriptional programs and greater role in R-loop formation. Utilizing new technologies to study promoter- enhancer connections, RNA:DNA interactions and transcriptional hubs mediated by RUNX1 this project will globally identify key RUNX1 targets regulating hematopoiesis. Additionally, the analysis of RUNX1 mediated R-loop formation will uncover RUNX1?s role in transcription/replication stress and contribution to DNA damage repair, demonstrated to constitute a key function in hematopoietic stem cell self-renewal and function.
The transcription factor RUNX1 is a master regulator of hematopoiesis, regulating the process where blood stem cells produce all mature cells in the blood system. Currently, RUNX1?s mechanistic roles transcription and promoter-enhancer interactions are poorly understood. This project aims to elucidate RUNX1?s function in these areas on a global scale and how disruption of RUNX1 leads to defective hematopoiesis.
