Current Biology
Volume 5, Issue 12, December 1995, Pages 1416-1423
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Research Paper
Physical interaction between a novel domain of the receptor Notch and the transcription factor RBP-Jκ/Su(H)

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Abstract

Background: The mammalian transcription factor RBP-Jκ binds to the DNA sequence motif CGTGGGAA and is involved in the regulation of gene expression; for example, it plays a part in the transactivation of viral and cellular genes by Epstein–Barr virus nuclear antigen-2. The Drosophila homologue of RBP-Jκ is the product of the Suppressor of Hairless(Su(H)) gene. Su(H) is a neurogenic gene that acts downstream of Notch, which encodes a cell-surface receptor. Furthermore, in the mouse, the phenotypes of homozygous mutant Notch 1 embryos are very similar to those of homozygous mutant RBP-Jκ embryos. Recent studies, using the yeast two-hybrid system, have led to the suggestion that the CDC10/ankyrin-like repeats of the Drosophila Notch protein interact with the Su(H) protein.

Results We searched for proteins that interact with mouse RBP-Jκ using the yeast two-hybrid system, and in this way identified a short intracellular region (mRAM23) of the mouse Notch1 protein that lacks any known sequence motif. In vitro interaction studies, using proteins fused to glutathione-S-transferase, showed that RBP-Jκ and Su(H) bind directly to the RAM23 regions of mouse Notch1 and Drosophila Notch, respectively. Immunoprecipitation analysis showed that RBP-Jκ and the mRAM23 region of mouse Notch1 also interact in vivo. Further studies, including site-directed mutagenesis experiments, narrowed down the region of mouse Notch1 that interacts with RBP-Jκ. The results indicate that this region is less than 50 amino-acid residues in length, and lies immediately downstream of the transmembrane region.

Conclusion We show that the transcription factor RBP-Jκ/Su(H) interacts directly with a novel intracellular domain of the cell-surface receptor Notch. RBP-Jκ/Su(H) does not appear to interact with Notch via the CDC10/ankyrin repeats implicated in previous studies.

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Kumiko Tamura, Yoshihito Taniguchi, Shigeru Minoguchi, Takashi Sakai, Tin Tun, Takahisa Furukawa and Tasuku Honjo (corresponding author), Department of Medical Chemistry, Kyoto University Faculty of Medicine, Yoshida, Sakyo-ku, Kyoto 606, Japan.

E-mail address for Tasuku Honjo: [email protected]