Localization of two antigenic determinants in histone H4

Area of Science:

• Molecular Biology
• Immunology
• Biochemistry

Background:

• Histone H4 is a core component of nucleosomes, playing a crucial role in DNA packaging and gene regulation.
• Understanding the antigenic properties of histone H4 is essential for studying autoimmune diseases and developing diagnostic tools.

Purpose of the Study:

• To map antigenic determinants on histone H4 using synthetic peptides.
• To investigate the accessibility of histone H4 epitopes in chromatin.

Main Methods:

• Solid-phase peptide synthesis was used to create four overlapping synthetic peptides of histone H4 (residues 80-102).
• Antigenic activity was assessed using complement fixation and enzyme-linked immunosorbent assays (ELISA) by inhibiting the H4-anti-H4 reaction.
• Antibody binding to free H4 and chromatin subunits was analyzed.

Main Results:

• One major antigenic determinant was localized to residues 88-96 of histone H4.
• Peptides 80-89 and 97-102 showed no antigenic activity.
• Antibodies generated against peptide 85-102 bound to free H4 but not to chromatin subunits, indicating reduced accessibility of the C-terminal region in nucleosomes.
• A second epitope was identified in the N-terminal region (1-53) of histone H4.

Conclusions:

• The C-terminal region of histone H4 contains at least one significant antigenic determinant (residues 88-96).
• The accessibility of the C-terminal region of histone H4 is limited within nucleosomes.
• Histone H4 possesses multiple antigenic sites, including one in the N-terminal region.