P 4 - Prof. Dr. Rudolf Grosschedl

Prof. Dr. Rudolf Grosschedl

MPI für Immunbiologie und Epigenetik, Freiburg

Stübeweg 51, 79108 Freiburg

Phone: +49 761 5108-711

Fax: + 49 761 5108-799

grosschedl@ie-freiburg.mpg.de

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Project Summary

This project addresses the mechanisms by which the functional specificity of the MAR-binding protein Satb2 can be altered by SUMO modification. We have previously shown that Satb2 plays important roles in the regulation of pluripotency of embryonic stem (ES) cells and in the higher-order chromatin structure of the immunoglobulin heavy chain gene locus in B cells. Recently, we found that Satb2 is SUMOylated during differentiation of ES cells, and in collaboration with the labs of Jorma Palvimo and Andrea Pichler, we identified Znf451 as a novel SUMO E3 ligase that mediates SUMOylation of Satb2 in a developmentally regulated manner. Importantly, we found that the knockdown of Znf451 impairs the differentiation of ES cells. In the next funding period, we will examine whether and how Znf451-mediated SUMOylation of Satb2 alters the function of Satb2 in regulating ES cell pluripotency. We will introduce SUMOylation-deficient Satb2 and covalently SUMO-modified Satb2 by gene knock-in into ES cells and examine the effects on differentiation, gene expression and higher-order chromatin structure. We will also analyze the effects of Satb2 in activation on higher-order chromatin structure in B lymphocytes. To gain insight into mechanism by which SUMOylation of Satb2 alters its functional specificity, we will examine the effects of SUMOylation on the interaction with previously identified Satb-binding partners. Finally, we will use a SILAC-based approach to assess differential binding of proteins to Satb2 and SUMOylated Satb2 in pluripotent and differentiating ES cells. Together, these experiments will shed light on the role of SUMOylation of Satb2 in the dynamics of ES cell self-renewal and differentiation.