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E-box variants direct formation of distinct complexes with the basic helix-loop-helix protein ALF1
B J Bonven1, A L Nielsen, P L Nørby
1Department of Molecular Biology, University of Aarhus, Denmark.
Journal of Molecular Biology
|June 9, 1995
Summary
Murine transcription factor ALF1 (a basic helix-loop-helix protein) interacts with E-box DNA sequences. Subtle DNA changes alter protein binding, impacting gene activation.
Area of Science:
- Molecular Biology
- Genetics
- Protein-DNA Interactions
Background:
- The murine transcription factor ALF1 is a basic helix-loop-helix (bHLH) protein.
- bHLH proteins recognize specific DNA sequences, known as E-boxes.
Purpose of the Study:
- To investigate how ALF1 binds to variations of the E-box DNA motif.
- To understand the impact of DNA sequence changes on protein-DNA interactions and transcriptional activity.
Main Methods:
- Binding site selection technology was employed to identify preferred DNA sequences.
- DNA modification interference analysis was used to map protein contact points on the DNA.
Main Results:
- Substitutions in non-conserved E-box positions significantly altered protein-DNA contacts.
- Differences in binding region extent and phosphate contact patterns were observed even for E-boxes with similar binding affinities.
- The identity of the base at the inner 'N' position critically influenced contact pattern specificity.
- E-box variants showed differential ability to mediate ALF1-dependent transcriptional activation in vivo.
Conclusions:
- Adaptability in bHLH protein-DNA interactions can lead to functional differences in protein-DNA complexes.
- The precise DNA sequence of the E-box is crucial for specifying protein contact patterns and transcriptional outcomes.