Structural studies of acetylated and control inner core histones

Area of Science:

• Molecular Biology
• Biochemistry
• Epigenetics

Background:

• Histones are fundamental proteins that package DNA into chromatin.
• Histone modifications, such as acetylation, are crucial epigenetic regulators.
• The inner core histone octamer's structure and function are key to gene regulation.

Purpose of the Study:

• To investigate the impact of acetylation on the conformation and association state of the inner core histone octamer.
• To understand how acetylation affects histone complex stability and secondary structure.
• To explore the implications of these changes for transcriptional control.

Main Methods:

• Development of a novel preparative procedure for isolating pure acetylated and control inner core histones from HeLa cells.
• Size-exclusion high-performance liquid chromatography (SE-HPLC) to assess association states.
• Sedimentation equilibrium studies to determine complex stability.
• Circular dichroism (CD) spectroscopy to analyze secondary structure (alpha-helix and beta-sheet content).

Main Results:

• Acetylated inner core histones associate into species larger than the octamer, forming more stable complexes compared to controls.
• Histone acetylation leads to an increased amount of alpha-helix, potentially linked to altered association states.
• Elevated temperatures and protein concentrations induce a greater increase in beta-sheet content in acetylated histones, possibly due to larger complex formation.

Conclusions:

• Acetylation significantly alters the conformation and association properties of the inner core histone octamer.
• The observed changes in conformational flexibility and association state of acetylated histones suggest a role in regulating nuclear transcription.
• These findings highlight acetylation as a critical factor influencing chromatin structure and function.