The RBP (Notch) corepressor complex in hematopoiesis
Final Report Abstract
The Notch signaling pathway regulates a broad spectrum of cell fate decisions and differentiation processes during embryogenesis and in postnatal development. The Notch signaling cascade is activated upon ligand binding, which leads to the translocation of the Notch intercellular domain (NICD) into the nucleus. There, the NICD binds to transcription factor RBP-J, recruits additional coactivators and activates transcription. In absence of Notch signaling, RBP-J represses Notch target genes by recruiting a corepressor complex. In this Emmy-Noether project, we have demonstrated that the central transcription factor in the Notch pathway, RBP-J, interacts in the absence of Notch signal with corepressor SHARP which in turn can recruit HDACs. We could subsequently identify a disease-link where leukemogenic fusion protein AML1/ETO is able to interfere with interaction between corepressors SHARP and ETO leading to derepression of Notch target genes. Furthermore, we examined Notch-based transcriptional regulation using a newly characterized pre-T cell line. We were able to show that target gene activation and repression in response to changes in Notch signalling is both highly dynamic and reversible. By switching-off and back-on Notch targets, we demonstrated that the active histone mark H3K4me3 is dynamically and specifically regulated at RBP-J binding sites. We found that the histone demethylase KDM5A directly interacts with RBP-J and is recruited to RBP-J binding sites in the absence of a Notch signal. Moreover, KDM5A augmented RBP-J-mediated repression and responses in vitro and in vivo in a Drosophila model of Notch-induced tumorigenesis. These findings indicate that dynamic regulation of histone methylation plays a key role in the Notch target gene expression and identify the histone demethylase KDM5A as a potential target in Notch-induced cancer therapies.
Publications
- (2003). Association of the Mediator with enhancers of active genes. P.N.A.S. 100(24):13887-91
Kuras, L., Borggrefe, T., Kornberg, RD.
- (2004): A unified nomenclature for protein subunits of Mediator complexes linking transcriptional regulators to RNA polymerase II. Mol. Cell 14(5):553-7
Henri-Marc Bourbon, Berk, A.J., Borggrefe, T., Conaway, J.W., Conaway, R.C., Freedman, L.P., Gustafsson, C.M., Hinnebusch, A.G., Holstege, F.C., Kim, Y.J., et al., Roeder, R.G. and Kornberg, R.D.
- (2004): The Mediator Complex in Transcriptional Regulation Research Advances in Biological Chemistry (2: 9-20)
Borggrefe, T.
- (2004): The sphingosine-1-phosphate lysophospholipid receptor S1P3 regulates MAdCAM-1+ endothelial cells in splenic marginal sinus organisation. J. Exp. Med. 200(11):1491-501
Girkontaite, I., Sakk, V., Wagner, M., Borggrefe, T., Tedford, K., Chun, J., and Fischer, K.D.
- (2005) RBP-Jkappa-SHARP recruit corepressors CtIP-CtBP to silence Notch target genes. Mol Cell Biol. (2005) 25(23):10379-90
Oswald, F., Winkler, M., Cao, Y., Astrahantseff, K., Bourtelle, S. Knöchel, W. and Borggrefe, T.
- (2006) The Mediator Complex Functions as a Coactivator for GATA-1 in Erythropoiesis via Subunit Med1/TRAP220. P.N.A.S. 103(49):18504-9
Stumpf, M., Waskow, C., Krötschel, M., van Essen, D., Rodriguez, P., Guyot, B., Roeder, R.G. and Borggrefe, T.
- (2008): ETO, but not leukemogenic fusion protein AML1/ETO, augments RBP-Jkappa/SHARP-mediated repression of notch target genes. Mol Cell Biol. (10):3502-12
Salat D, Liefke R, Wiedenmann J, Borggrefe T, Oswald F
- (2009): The Notch signaling pathway: Transcriptional regulation at Notch target genes. Cellular and Molecular Life Sciences 66(10):1631-46
Borggrefe, T. and Oswald, F.
- (2010): Histone demethylase KDM5A is an integral part of the core Notch-RBP-J repressor complex. Genes&Development, 24(6):590-601
Liefke, R., Oswald, F., Alvarado, C., Ferres-Marco, D., Mittler, G., Rodriguez, P., Dominguez, M. and Borggrefe, T.
