Transcription preinitiation complex structure and dynamics provide insight into genetic diseases

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• Transcription preinitiation complexes (PICs) are essential for gene expression.
• Previous cryo-electron microscopy (cryo-EM) studies provided partial structural insights.
• Incompletely modeled regions hindered functional analysis of PICs.

Purpose of the Study:

• To integrate available cryo-EM data for a complete human PIC structural model.
• To investigate the dynamics and functional mechanisms of the PIC.
• To correlate disease mutations with specific functional defects within the PIC.

Main Methods:

• Integration of all available cryo-EM data to build a comprehensive human PIC model.
• Molecular dynamics simulations to analyze global motions and dynamic communities.
• Mapping of disease mutations onto the structural model.

Main Results:

• A practically complete human PIC structural model was constructed.
• Simulations revealed global motions, dynamic communities, and DNA remodeling mechanisms.
• Key TFIIE-p62 interactions linking core-PIC to TFIIH were identified.
• p62 was shown to interlace TFIIH subunits (p34, p44, XPD) and cap XPD's DNA/ATP sites.
• PIC structure facilitates DNA kinking and negative supercoiling for promoter opening.
• Disease mutations cluster into three mechanistic classes affecting TFIIH function and interactions.

Conclusions:

• The integrated structural model provides unprecedented insights into PIC assembly and function.
• Understanding PIC dynamics and DNA interactions is crucial for gene regulation.
• The study elucidates mechanistic bases for diseases linked to PIC dysfunction, including xeroderma pigmentosum, trichothiodystrophy, and Cockayne syndrome.