Definitive hematopoiesis requires Runx1 C-terminal-mediated subnuclear targeting and transactivation

Abstract

Runx1 is a key hematopoietic transcription factor required for definitive hematopoiesis and is a frequent target of leukemia-related chromosomal translocations. The resulting fusion proteins, while retaining DNA binding activity, display loss of subnuclear targeting and associated transactivation functions encoded by the C-terminus of the protein. To define the precise contribution of the Runx1 C-terminus in development and leukemia, we created a knock-in mouse with a C-terminal truncation by introducing a single nucleic acid substitution in the native Runx1 locus. This mutation (Runx1(Q307X)) models genetic lesions observed in patients with leukemia and myeloproliferative disorders. The Runx1(Q307X) homozygous mouse exhibits embryonic lethality at E12.5 due to central nervous system hemorrhages and a complete lack of hematopoietic stem cell function. While able to bind DNA, Runx1(Q307X) is unable to activate target genes, resulting in deregulation of various hematopoietic markers. Thus, we demonstrate that the subnuclear targeting and transcriptional regulatory activities of the Runx1 C-terminus are critical for hematopoietic development. We propose that compromising the C-terminal functions of Runx1 is a common mechanism for the pathological consequences of a variety of somatic mutations and Runx1-related leukemic fusion proteins observed in human patients.

Dynamic shifts in occupancy by TAL1 are guided by GATA factors and drive large-scale reprogramming of gene expression during hematopoiesis

“…Cell-specific binding of TAL1 and associated proteins target different cohorts of genes. (Okuda et al 1996;Dowdy et al 2010) and its down-regulation in erythroid cells (Lorsbach et al 2004;North et al 2004). Other TFs that cobind frequently with TAL1 in erythroid cells are members of the pentameric complex.…”

Transcriptional regulation and spatial organisation of the human AML1/RUNX1 gene

“…and Goldfarb, 2007;Ito, 2008;Dowdy et al, 2010], the mechanism directing the tissue-specific expression of the non-rearranged human RUNX1 gene remains unclear. This gene was shown to be highly active in the haematopoietic system but not in other tissues (brain, lung, ovaries and testis) [Levanon et al, 1994Nucifora and Rowley, 1995].…”

RUNX1 Mutations in Clonal Myeloid Disorders: From Conventional Cytogenetics to Next Generation Sequencing, A Story 40 Years in the Making

“…13–16 No structures of this domain have been solved, although computational analysis 17 predicts that parts of the transactivation domain and an adjacent inhibitory domain are likely to be structured. Multiple proteins have been identified that interact with sequences C-terminal to the Runt domain that presumably mediate its activities.…”