Nucleosome Engagement Regulates RORγt Structure and Dynamics

Area of Science:

• Immunology
• Molecular Biology
• Structural Biology

Background:

• Retinoic acid-related orphan receptor gamma (RORγt) is crucial for Th17 cell development and immune responses.
• RORγt binds DNA response elements to activate gene expression, but its interaction with chromatin is not well understood.

Purpose of the Study:

• To investigate how the nucleosome, a fundamental unit of chromatin, affects RORγt binding, structure, and function.
• To elucidate the mechanisms by which RORγt interacts with chromatinized DNA to regulate gene expression.

Main Methods:

• Nucleosome accessibility profiling to determine RORγt binding sites on DNA.
• Hydrogen deuterium exchange coupled with mass spectrometry (HDX-MS) to study RORγt dynamics and allosteric effects.
• High-resolution structural analysis of RORγt bound to nucleosomes.

Main Results:

• RORγt preferentially binds to free DNA and nucleosome entry/exit sites with single base-pair resolution.
• Allosteric effects influencing RORγt binding and chromatin dynamics were identified.
• A high-resolution structure revealed how RORγt specifically binds to chromatin substrates.

Conclusions:

• RORγt binding to chromatinized DNA promotes coregulator recruitment and chromatin decompaction.
• This study provides a mechanistic understanding of RORγt function within the chromatin environment.
• Findings offer insights into adaptive immunity regulation by RORγt.