Physical association of the patient-specific GATA1 mutants with RUNX1 in acute megakaryoblastic leukemia accompanying Down syndrome

Abstract

Mutations of the GATA1 gene on chromosome X have been found in almost all cases of transient myeloproliferative disorder and acute megakaryoblastic leukemia (AMKL) accompanying Down syndrome (DS). Although most GATA1 mutations lead to the expression of GATA1s lacking the N-terminal activation domain, we recently found two novel GATA1 proteins with defects in another N-terminal region. It has been suggested that loss of the N-terminal portion of GATA1 might interfere with physiological interactions with the critical megakaryocytic transcription factor RUNX1, and this would imply that GATA1s is not able to interact properly with RUNX1. However, the interaction domain of GATA1 remains controversial. In this study, we show that GATA1 binds to RUNX1 through its zinc-finger domains, and that the C-finger is indispensable for synergy with RUNX1. All of the patient-specific GATA1 mutants interacted efficiently with RUNX1 and retained their ability to act synergistically with RUNX1 on the megakaryocytic GP1ba promoter, whereas the levels of transcriptional activities were diverse among the mutants. Thus, our data indicate that physical interaction and synergy between GATA1 and RUNX1 are retained in DS-AMKL, although it is still possible that increased RUNX1 activity plays a role in the development of leukemia in DS.

Global transcriptome and chromatin occupancy analysis reveal the short isoform of GATA1 is deficient for erythroid specification and gene expression

“…45 Furthermore, a different study indicated the RUNX-GATA1 interaction occurs through the zinc finger domains and is maintained by the GATA1s isoform. 46 Another study demonstrated an interaction with pRB that is ablated by the GATA1s mutation and further revealed that the protein-protein interaction is required for cell cycle arrest during terminal erythroid differentiation. 47 Loss of the Rb interaction is also thought to contribute to leukemic transformation in DS-AMKL through increased E2F activity.…”

Concurrent transcriptional deregulation of AML1/RUNX1 and GATA factors by the AML1-TRPS1 chimeric gene in t(8;21)(q24;q22) acute myeloid leukemia

“…However, these DNA-binding mutants still retained significant repressive activity (compare bars 2, 5, and 8 in Figure 2E and bars 2, 5, and 11 in Figure 2F), and AT/R174Q and AT/GATAm even showed decreased suppression in the M␣P and BXH2-LTR reporter assays, respectively, in a dose-dependent manner (bars 6-8 in Figure 2F and bars 9-11 in Figure 2E). Since AML1 is known to physically interact with GATA-1 through its Runt domain, [20][21][22] the chimera may also bind to GATA-1. As expected, in an immunoprecipitation experiment, wild-type AML1 interacted with GATA-1, while the AML1 R174Q mutant did not ( Figure 2H).…”

Transcriptional control of megakaryocyte development

“…Shared target genes include C-MPL, GPIba, JAK2 and GPIIb (Vyas et al, 1999;Heller et al, 2005;Kuhl et al, 2005;Muntean and Crispino, 2005;Liu et al, 2006;Xu et al, 2006). Biochemical studies have demonstrated physical interaction and functional cooperation of these two factors in transcriptional activation of megakaryocytic promoters (Elagib et al, 2003;Xu et al, 2006). Their crosstalk reflects a highly conserved pathway in evolution, with parallels found in the Drosophila GATA and RUNX counterparts, Serpent and Lozenge, which cooperate in the programming of hematopoietic crystal cell development (Fossett et al, 2003;Waltzer et al, 2003).…”

“…In both, the megakaryocytes display immature morphology, diminished ploidy, increased colony forming capabilities, increased proliferation and defective formation of demarcation membranes (Vyas et al, 1999;Nichols et al, 2000;Walker et al, 2002;Ichikawa et al, 2004;Growney et al, 2005;Heller et al, 2005;Hollanda et al, 2006). Shared target genes include C-MPL, GPIba, JAK2 and GPIIb (Vyas et al, 1999;Heller et al, 2005;Kuhl et al, 2005;Muntean and Crispino, 2005;Liu et al, 2006;Xu et al, 2006). Biochemical studies have demonstrated physical interaction and functional cooperation of these two factors in transcriptional activation of megakaryocytic promoters (Elagib et al, 2003;Xu et al, 2006).…”