Multiple phosphorylation sites are important for RUNX1 activity in early hematopoiesis and T-cell differentiation

Department of Hematology & Oncology, Graduate School of Medicine, University of Tokyo, Tokyo, Japan.
European Journal of Immunology (Impact Factor: 4.03). 04/2012; 42(4):1044-50. DOI: 10.1002/eji.201040746
Source: PubMed


RUNX1 is essential for definitive hematopoiesis and T-cell differentiation. It has been shown that RUNX1 is phosphorylated at specific serine and threonine residues by several kinase families. However, it remains unclear whether RUNX1 phosphorylation is absolutely required for its biological functions. Here, we evaluated hematopoietic activities of RUNX1 mutants with serine (S)/threonine (T) to alanine (A), aspartic acid (D), or glutamic acid (E) mutations at phosphorylation sites using primary culture systems. Consistent with the results of knockin mice, RUNX1-2A, carrying two phospho-deficient mutations at S276 and S293, retained hematopoietic activity. RUNX1-4A, carrying four mutations at S276, S293, T300, and S303, showed impaired T-cell differentiation activity, but retained the ability to rescue the defective early hematopoiesis of Runx1-deficient cells. Notably, RUNX1-5A, carrying five mutations at S276, S293, T300, S303, and S462, completely lost its hematopoietic activity. In contrast, the phospho-mimic proteins RUNX1-4D/E and RUNX1-5D/E exhibited normal function. Our study identifies multiple phosphorylation sites that are indispensable for RUNX1 activity in hematopoiesis.

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Available from: Takashi Asai,
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    • "But how, then, are seryl/threonyl and tyrosyl phosphorylation coordinated during differentiation , especially as they seem to have opposing effects? Seryl/threonyl phosphorylation appears to be necessary for Runx1 to drive T-cell differentiation and Cd4 silencing (Yoshimi et al. 2012), whereas Huang et al. (2012) found Figure 2. Runx1 preferentially interacts with the SWI/SNF Brg1 and Snf5 subunits when tyrosyl phosphorylated by SFKs and interacts with the transcriptional coregulators Gata1, Fli-1, and CBFb when unphosphorylated by Shp2. Whether or not tyrosyl phosphorylated Runx1 actively promotes proliferation is unknown. "
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    ABSTRACT: The Runx1 transcription factor is post-translationally modified by seryl/threonyl phosphorylation, acetylation, and methylation that control its interactions with transcription factor partners and epigenetic coregulators. In this issue of Genes & Development, Huang and colleagues (pp. 1587-1601) describe how the regulation of Runx1 tyrosyl phosphorylation by Src family kinases and the Shp2 phosphatase toggle Runx1's interactions between different coregulatory molecules.
    Genes & development 07/2012; 26(14):1520-6. DOI:10.1101/gad.198051.112 · 10.80 Impact Factor
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    ABSTRACT: Since its discovery from a translocation in leukemias, the runt-related transcription factor 1/acute myelogenous leukemia-1 (RUNX1/AML1), which is widely expressed in hematopoietic cells, has been extensively studied. Many lines of evidence have shown that RUNX1 plays a critical role in regulating the development and precise maintenance of mammalian hematopoiesis. Studies using knockout mice have shown the importance of RUNX1 in a wide variety of hematopoietic cells, including hematopoietic stem cells and megakaryocytes. Recently, target molecular processes of RUNX1 in normal and malignant hematopoiesis have been revealed. Although RUNX1 is not required for the maintenance of hematopoietic stem cells, it is required for the homeostasis of hematopoietic stem and progenitor cells, and expansion of hematopoietic stem and progenitor cells due to RUNX1 deletion may be an important cause of human leukemias. Molecular abnormalities cooperating with loss of RUNX1 have also been identified. These findings may lead to a further understanding of human leukemias, and suggest novel molecular targeted therapies in the near future.
    International journal of hematology 04/2013; 97(6). DOI:10.1007/s12185-013-1347-3 · 1.92 Impact Factor
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    ABSTRACT: The transcription factor Runx1 has been studied in leukemia and blood for decades, but recently it has been also implicated in epithelial biology and pathology. Particularly in mouse skin Runx1 modulates Wnt signaling levels thereby regulating timely induction of hair follicle specification, proper maturation of the emerging adult hair follicle stem cells in embryogenesis, and timely stem cell (SC) activation during adult homeostasis. Moreover, Runx1 acts as a tumor promoter in mouse skin squamous tumor formation and maintenance, likely by repressing p21 and promoting Stat3 activation. Similarly, Runx1 is essential for oral epithelium tumorigenesis mediated in mice by Ras, and for growth of three kinds of human epithelial cancer cells. In contrast, Runx1 has a tumor suppressor function in the mouse intestine and shows tumor subtype specific behavior in human breast cancer. Multiple studies revealed Runx1 SNPs to be associated with human cancers and autoimmune disease. With this information as background, the field is poised for functional and mechanistic studies to elucidate the role of Runx1 in formation and/or progression of epithelial-based human disease. J. Cell. Biochem. © 2012 Wiley Periodicals, Inc.
    Journal of Cellular Biochemistry 05/2013; 114(5). DOI:10.1002/jcb.24453 · 3.26 Impact Factor
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