The basic helix-loop-helix-zipper domain of TFE3 mediates enhancer-promoter interaction.
Mol Cell Biol
; 14(12): 7704-16, 1994 Dec.
Article
in En
| MEDLINE
| ID: mdl-7969114
ABSTRACT
Binding sites for three families of sequence-specific DNA-binding proteins, microE3, C/EBP, and OCT, are found in both the promoters and the intronic enhancer of the immunoglobulin heavy-chain gene. We have used a cotransfection system to investigate how proteins binding these sites may participate in enhancer-promoter interactions. Basic helix-loop-helix-zipper (BHLHZIP) proteins TFE3 and TFEB activate from a distance in this assay, but the basic zipper (BZIP) protein NF-IL6 and endogenous OCT-binding proteins do not. Our results suggest that remotely bound TFE3 is recruited to the initiation site by association with proximally bound TFE3; this interaction is mediated by the BHLHZIP domain and not by activation domains of TFE3. The BZIP domain of Ig/EBP lacks this activity, revealing an important functional difference between these structurally related dimerization domains. We also show that TFE3 can exist as a tetramer in solution and that tetramerization is determined by the HLHZIP domain. These data support a model in which protein-protein interactions between proximally and remotely bound TFE3 recruit TFE3 to the initiation site for activation. The IgH gene is the first example of a cellular gene in which proximal and distal binding sites are found for a protein capable of mediating enhancer-promoter interaction.
Full text:
1
Database:
MEDLINE
Main subject:
Transcription Factors
/
Gene Expression Regulation
/
Enhancer Elements, Genetic
/
Promoter Regions, Genetic
/
DNA-Binding Proteins
Type of study:
Prognostic_studies
Limits:
Animals
Language:
En
Journal:
Mol Cell Biol
Year:
1994
Type:
Article