GATA3-Controlled Nucleosome Eviction Drives <i>MYC</i> Enhancer Activity in T-cell Development and Leukemia

Abstract

Long-range enhancers govern the temporal and spatial control of gene expression; however, the mechanisms that regulate enhancer activity during normal and malignant development remain poorly understood. Here, we demonstrate a role for aberrant chromatin accessibility in the regulation of <i>MYC</i> expression in T-cell lymphoblastic leukemia (T-ALL). Central to this process, the NOTCH1-<i>MYC</i> enhancer (N-Me), a long-range T cell-specific <i>MYC</i> enhancer, shows dynamic changes in chromatin accessibility during T-cell specification and maturation and an aberrant high degree of chromatin accessibility in mouse and human T-ALL cells. Mechanistically, we demonstrate that GATA3-driven nucleosome eviction dynamically modulates N-Me enhancer activity and is strictly required for NOTCH1-induced T-ALL initiation and maintenance. These results directly implicate aberrant regulation of chromatin accessibility at oncogenic enhancers as a mechanism of leukemic transformation. SIGNIFICANCE: <i>MYC</i> is a major effector of NOTCH1 oncogenic programs in T-ALL. Here, we show a major role for GATA3-mediated enhancer nucleosome eviction as a driver of <i>MYC</i> expression and leukemic transformation. These results support the role of aberrant chromatin accessibility and consequent oncogenic <i>MYC</i> enhancer activation in NOTCH1-induced T-ALL.<i>This article is highlighted in the In This Issue feature, p. 1631</i>.