The TAL1 complex targets the FBXW7 tumor suppressor by activating miR-223 in human T cell acute lymphoblastic leukemia

• Main Authors: Mansour, Marc R. (Author), Sanda, Takaomi (Author), Lawton, Lee N. (Author), Li, Xiaoyu (Author), Kreslavsky, Taras (Author), Novina, Carl D. (Author), Brand, Marjorie (Author), Gutierrez, Alejandro (Author), Kelliher, Michelle A. (Author), Jamieson, Catriona H. M. (Author), von Boehmer, Harald (Author), Young, Richard A. (Contributor), Look, A. Thomas (Author)
• Other Authors: Massachusetts Institute of Technology. Department of Biology (Contributor)
• Format: Article
• Language: English
• Published: Rockefeller University Press, 2014-09-02T14:30:25Z.
• Subjects: Article
• Online Access: Get fulltext

The oncogenic transcription factor TAL1/SCL is aberrantly expressed in 60% of cases of human T cell acute lymphoblastic leukemia (T-ALL) and initiates T-ALL in mouse models. By performing global microRNA (miRNA) expression profiling after depletion of TAL1, together with genome-wide analysis of TAL1 occupancy by chromatin immunoprecipitation coupled to massively parallel DNA sequencing, we identified the miRNA genes directly controlled by TAL1 and its regulatory partners HEB, E2A, LMO1/2, GATA3, and RUNX1. The most dynamically regulated miRNA was miR-223, which is bound at its promoter and up-regulated by the TAL1 complex. miR-223 expression mirrors TAL1 levels during thymic development, with high expression in early thymocytes and marked down-regulation after the double-negative-2 stage of maturation. We demonstrate that aberrant miR-223 up-regulation by TAL1 is important for optimal growth of TAL1-positive T-ALL cells and that sustained expression of miR-223 partially rescues T-ALL cells after TAL1 knockdown. Overexpression of miR-223 also leads to marked down-regulation of FBXW7 protein expression, whereas knockdown of TAL1 leads to up-regulation of FBXW7 protein levels, with a marked reduction of its substrates MYC, MYB, NOTCH1, and CYCLIN E. We conclude that TAL1-mediated up-regulation of miR-223 promotes the malignant phenotype in T-ALL through repression of the FBXW7 tumor suppressor.
National Cancer Institute (U.S.) (5P01CA109901)
National Cancer Institute (U.S.) (5P01CA68484)
National Cancer Institute (U.S.) (1K99CA157951)
National Institutes of Health (U.S.). Intramural Research Program
Center for Cancer Research (National Cancer Institute (U.S.))