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J. Biol. Chem., Vol. 282, Issue 22, 16164-16176, June 1, 2007

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HoxA10 Activates Transcription of the Gene Encoding Mitogen-activated Protein Kinase Phosphatase 2 (Mkp2) in Myeloid Cells^*

Hao Wang, YuFeng Lu, Weiqi Huang, E. Terry Papoutsakis^¶, Peter Fuhrken^¶, and Elizabeth A. Eklund¹

From the Fineberg School of Medicine and the Robert H. Lurie Comprehensive Cancer Center, Northwestern University, Chicago, Illinois 60611, the ^¶Department of Chemical and Biological Engineering, Northwestern University, Chicago, Illinois 60208, and Jesse Brown Veterans Affairs Medical Center, Chicago, Illinois 60612

HoxA10 is a homeodomain transcription factor that is frequently overexpressed in human acute myeloid leukemia. In murine bone marrow transplantation studies, HoxA10 overexpression induces a myeloproliferative disorder with accumulation of mature phagocytes in the peripheral blood and tissues. Over time, differentiation block develops in these animals, resulting in acute myeloid leukemia. In immature myeloid cells, HoxA10 represses transcription of some genes that confer the mature phagocyte phenotype. Therefore, overexpressed HoxA10 blocks differentiation by repressing myeloid-specific gene transcription in differentiating myeloid cells. In contrast, target genes involved in myeloproliferation due to HoxA10 overexpression have not been identified. To identify such genes, we screened a CpG island microarray with HoxA10 co-immunoprecipitating chromatin. We identified the DUSP4 gene, which encodes mitogen-activated protein kinase phosphatase 2 (Mkp2), as a HoxA10 target gene. We analyzed the DUSP4 5'-flank and identified two proximal-promoter cis elements that are activated by HoxA10. We find that DUSP4 transcription and Mkp2 expression decrease during normal myelopoiesis. However, this down-regulation is impaired in myeloid cells overexpressing HoxA10. In hematopoietic cells, c-Jun N-terminal kinases (Jnk) are the preferred substrates for Mkp2. Therefore, Mkp2 inhibits apoptosis by dephosphorylating (inactivating) Jnk. Consistent with this, HoxA10 overexpression decreases apoptosis in differentiating myeloid cells. Therefore, our studies identify a mechanism by which overexpressed HoxA10 contributes to inappropriate cell survival during myelopoiesis.

Received for publication, November 14, 2006 , and in revised form, March 8, 2007.

^* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

¹ To whom correspondence should be addressed: Feinberg School of Medicine at Northwestern University, 710 N. Fairbanks Ct., Olson 8524, Chicago, IL 60611. Tel.: 312-503-4625; E-mail: e-eklund{at}northwestern.edu.

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