Myeloid Translocation Gene 16 (MTG16) Interacts with Notch Transcription Complex Components To Integrate Notch Signaling in Hematopoietic Cell Fate Specification

Abstract

The Notch signaling pathway regulates gene expression programs to influence the specification of cell fate in diverse tissues. In response to ligand binding, the intracellular domain of the Notch receptor is cleaved by the γ-secretase complex and then translocates to the nucleus. There, it binds the transcriptional repressor CSL, triggering its conversion to an activator of Notch target gene expression. The events that control this conversion are poorly understood. We show that the transcriptional corepressor, MTG16, interacts with both CSL and the intracellular domains of Notch receptors, suggesting a pivotal role in regulation of the Notch transcription complex. The Notch1 intracellular domain disrupts the MTG16-CSL interaction. Ex vivo fate specification in response to Notch signal activation is impaired in Mtg16^−/− hematopoietic progenitors, and restored by MTG16 expression. An MTG16 derivative lacking the binding site for the intracellular domain of Notch1 fails to restore Notch-dependent cell fate. These data suggest that MTG16 interfaces with critical components of the Notch transcription complex to affect Notch-dependent lineage allocation in hematopoiesis.

Supplemental material for this article may be found at http://mcb.asm.org/.

We are indebted to Thao Dang, Warren Pear, Jan Kitajewski, Jennifer Pietenpol, Juan Carlos Zúñiga Pflücker, and Al Reynolds for their gifts of reagents. We gratefully acknowledge our colleagues Christopher Williams, Utpal Davé, Joseph Amann, and Steve Brandt for their critical evaluation and thoughtful suggestions regarding the manuscript.

We also thank the Vanderbilt Monoclonal Antibody and Vanderbilt Flow Cytometry shared resource facilities for their assistance (supported by NIH grants P30 CA68485 and DK058404). Cell imaging studies were performed in part through the use of the Vanderbilt University Medical Center Cell Imaging shared resource (supported by NIH grants CA68485, DK20593, DK58404, HD15052, DK59637, and Ey008126). M.E.E. is a recipient of a young investigator award from Alex's Lemonade Stand Pediatric Research Foundation, a Hyundai Scholar award from the Hyundai Automotive Corporation, and a career development award from the St. Baldrick's Foundation for Pediatric Cancer Research. J.M. is a recipient of a medical student research fellowship from the Howard Hughes Medical Institute. The work is supported in part by National Institutes of Health grants F32 CA119859 (M.E.E.), F30 HL093993 (A.H.), and R01 HL088494 (S.W.H.).

We declare no competing financial interests.