Structural requirements for assembly of the CSL.intracellular Notch1.Mastermind-like 1 transcriptional activation complex.
Ligand binding by Notch receptors triggers a series of proteolytic cleavages that liberate the intracellular portion of Notch (ICN) from the cell membrane, permitting it to translocate to the nucleus. Nuclear ICN binds to a highly conserved DNA-binding transcription factor called CSL (also known as RBP-Jkappa, CBF1, Suppressor of Hairless, ... and Lag-1) and recruits Mastermind-like transcriptional co-activators to form a transcriptional activation complex. Using bioinformatics tools, we identified a Rel homology region (RHR) within CSL that was used as a guide to determine the minimal protein requirements for ternary complex formation. The RHR of CSL contains both the N- and C-terminal beta-sheet domains (RHR-n and RHR-c) of typical Rel transcription factors, as judged by circular dichroism spectra. Binding of monomeric CSL to DNA requires the entire RHR of CSL and an additional 125-residue N-terminal sequence, whereas binding to ICN requires only the RHR-n domain. Although the RAM (RBP-Jkappa (recombination-signal-sequence-binding protein for Jkappa genes)-associated molecule) domain of ICN is flexible and relatively unstructured as an isolated polypeptide in solution, it associates stably with CSL on DNA. Recruitment of Mastermind-like 1 (MAML1) to CSL.ICN complexes on DNA requires inclusion of the ankyrin repeat domain of ICN, and N- and C-terminal sequences of CSL extending beyond the DNA-binding region. The requirement for cooperative assembly of the MAML1.ICN.CSL.DNA complex suggests that a primary function of ICN is to render CSL competent for MAML loading. On the basis of our results, we present a working structural model for the organization of the MAML1.ICN.CSL.DNA complex.
Mesh Terms:
Ankyrins, Biophysical Phenomena, Biophysics, DNA, DNA-Binding Proteins, Humans, Immunoglobulin J Recombination Signal Sequence-Binding Protein, Membrane Proteins, Molecular Sequence Data, Nuclear Proteins, Protein Structure, Tertiary, Proto-Oncogene Proteins c-rel, Receptor, Notch1, Receptors, Cell Surface, Sequence Homology, Amino Acid, Structure-Activity Relationship, Trans-Activators, Transcription Factors, Transcriptional Activation
Ankyrins, Biophysical Phenomena, Biophysics, DNA, DNA-Binding Proteins, Humans, Immunoglobulin J Recombination Signal Sequence-Binding Protein, Membrane Proteins, Molecular Sequence Data, Nuclear Proteins, Protein Structure, Tertiary, Proto-Oncogene Proteins c-rel, Receptor, Notch1, Receptors, Cell Surface, Sequence Homology, Amino Acid, Structure-Activity Relationship, Trans-Activators, Transcription Factors, Transcriptional Activation
J. Biol. Chem.
Date: Jun. 06, 2003
PubMed ID: 12644465
View in: Pubmed Google Scholar
Download Curated Data For This Publication
7990
Switch View:
- Interactions 1