GATA2 regulates the erythropoietin receptor in t(12;21) ALL
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Marie E. Gaine1,2,*, Daniel J. Sharpe1,*, James S. Smith1, Hilary A.A. Colyer1, Vivien M. Hodges1, Terry R. Lappin1 and Ken I. Mills1
1Centre for Cancer Research and Cell Biology, Queen’s University Belfast, Belfast BT9 7BL, United Kingdom
2Current/Present address: Department of Molecular Physiology and Biophysics, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA
*These two authors have contributed equally to the manuscript
Ken I. Mills, email: firstname.lastname@example.org
Keywords: EPOR, GATA2, acute lymphoblastic leukemia, epigenetic, transcriptional regulation
Received: April 11, 2017 Accepted: June 26, 2017 Published: August 02, 2017
The t(12;21) (p13;q22) chromosomal translocation resulting in the ETV6/RUNX1 fusion gene is the most frequent structural cytogenetic abnormality in children with acute lymphoblastic leukemia (ALL). The erythropoietin receptor (EPOR), usually associated with erythroid progenitor cells, is highly expressed in ETV6/RUNX1 positive cases compared to other B-lineage ALL subtypes. Gene expression analysis of a microarray database and direct quantitative analysis of patient samples revealed strong correlation between EPOR and GATA2 expression in ALL, and higher expression of GATA2 in t(12;21) patients. The mechanism of EPOR regulation was mainly investigated using two B-ALL cell lines: REH, which harbor and express the ETV6/RUNX1 fusion gene; and NALM-6, which do not. Expression of EPOR was increased in REH cells compared to NALM-6 cells. Moreover, of the six GATA family members only GATA2 was differentially expressed with substantially higher levels present in REH cells. GATA2 was shown to bind to the EPOR 5'-UTR in REH, but did not bind in NALM-6 cells. Overexpression of GATA2 led to an increase in EPOR expression in REH cells only, indicating that GATA2 regulates EPOR but is dependent on the cellular context. Both EPOR and GATA2 are hypomethylated and associated with increased mRNA expression in REH compared to NALM-6 cells. Decitabine treatment effectively reduced methylation of CpG sites in the GATA2 promoter leading to increased GATA2 expression in both cell lines. Although Decitabine also reduced an already low level of methylation of the EPOR in NALM-6 cells there was no increase in EPOR expression. Furthermore, EPOR and GATA2 are regulated post-transcriptionally by miR-362 and miR-650, respectively. Overall our data show that EPOR expression in t(12;21) B-ALL cells, is regulated by GATA2 and is mediated through epigenetic, transcriptional and post-transcriptional mechanisms, contingent upon the genetic subtype of the disease.
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