Tuning Transcription Factor Availability through Acetylation-Mediated Genomic Redistribution

Area of Science:

• Molecular Biology
• Cell Biology
• Cancer Biology

Background:

• Transcription factors typically bind DNA with high affinity to regulate gene expression.
• In vivo, transcription factors encounter numerous low-affinity, degenerate motifs alongside specific binding sites.
• The role of low-affinity binding sites and post-translational modifications in transcription factor regulation remains incompletely understood.

Purpose of the Study:

• To investigate the role of transcription factor DNA-binding affinity and acetylation in regulating transcription initiation.
• To elucidate the mechanism by which transcription factors access and occupy regulatory elements in vivo.
• To understand the function of the melanoma lineage survival oncogene MITF in melanocyte development and tumorigenesis.

Main Methods:

• Utilized the melanoma lineage survival oncogene MITF as a model system.
• Investigated the impact of low-affinity binding sites and MAPK-stimulated acetylation on transcription factor availability.
• Analyzed acetylation-mimetic and non-acetylatable MITF mutants with varying DNA-binding affinities.

Main Results:

• Demonstrated that low-affinity binding sites serve as a competitive reservoir for transcription factors in vivo.
• Showed that mitogen-activated protein kinase (MAPK)-stimulated acetylation releases transcription factors from this reservoir, enhancing regulatory element occupancy.
• Found that a low-affinity, acetylation-mimetic MITF mutant promotes melanocyte development and tumorigenesis, unlike a high-affinity, non-acetylatable mutant.

Conclusions:

• Revealed an acetylation-mediated molecular clutch mechanism that regulates transcription factor availability through genome-wide redistribution.
• Established a link between BRAF signaling, acetylation, and tumorigenesis via MITF.
• Suggested that p300/CREB-binding protein-mediated transcription factor acetylation is a common regulatory mechanism controlling transcription factor availability.