Mammalian Trithorax and Polycomb-group homologues are antagonistic regulators of homeotic development

Robin D. Hanson, Jay L. Hess, Benjamin D. Yu, Patricia Ernst, Maarten Van Lohuizen, Anton Berns, Nathalie M.T. Van Der Lugt, Cooduvalli S. Shashikant, Frank H. Ruddle, Masao Seto, Stanley J. Korsmeyer

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211 Scopus citations


Control of cell identity during development is specified in large part by the unique expression patterns of multiple homeobox-containing (Hox) genes in specific segments of an embryo. Trithorax and Polycomb-group (Trx-G and Pc-G) proteins in Drosophila maintain Hox expression or repression, respectively. Mixed lineage leukemia (MLL) is frequently involved in chromosomal translocations associated with acute leukemia and is the one established mammalian homologue of Trx. Bmi-1 was first identified as a collaborator in c-myc-induced murine lymphomagenesis and is homologous to the Drosophila Pc-G member Posterior sex combs. Here, we note the axial-skeletal transformations and altered Hox expression patterns of MII-deficient and Bmi- 1-deficient mice were normalized when both MII and Bmi-1 were deleted, demonstrating their antagonistic role in determining segmental identity. Embryonic fibroblasts from MII-deficient compared with Bmi-1-deficient mice demonstrate reciprocal regulation of Hox genes as well as an integrated Hoxc8-lacZ reporter construct. Reexpression of MLL was able to overcome repression, rescuing expression of Hoxc8-lacZ in MII-deficient cells. Consistent with this, MLL and BMI-I display discrete subnuclear colocalization. Although Drosophila Pc-G and Trx-G members have been shown to maintain a previously established transcriptional pattern, we demonstrate that MLL can also dynamically regulate a target Hox gene.

Original languageEnglish (US)
Pages (from-to)14372-14377
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number25
StatePublished - Dec 7 1999

All Science Journal Classification (ASJC) codes

  • General


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