Histones bundle F-actin filaments and affect actin structure.

Area of Science:

• Biochemistry
• Cell Biology
• Biophysics

Background:

• Histones are nuclear proteins secreted during apoptosis and necrosis.
• Extracellular histones interact with polyanionic compounds like actin.
• Actin polymerization and bundling are crucial cellular processes.

Purpose of the Study:

• To investigate the interaction between histones and actin.
• To characterize the properties of histone-actin complexes.
• To explore the potential role of histone-actin interactions in cystic fibrosis.

Main Methods:

• Studied histone mixture (histone type III) and recombinant H2A histone interactions with G-actin and F-actin.
• Assessed the effect of ionic strength, DNA, DNase1, and cofilin on histone-actin bundles.
• Measured changes in solution viscosity and light scattering.
• Utilized low-speed centrifugation to quantify F-actin.

Main Results:

• Histones (type III and H2A) bundle F-actin, polymerize G-actin, and increase solution viscosity.
• Histone-actin bundles exhibit greater stability against ionic strength changes compared to other polycations.
• DNA disassembles histone-actin bundles, while DNase1 and cofilin have differential effects.
• Stable histone-actin bundles are found in cystic fibrosis sputum, suggesting a role in disease pathology.

Conclusions:

• Histones bind tightly to F-actin via strong electrostatic and hydrophobic forces.
• Stable histone-actin bundles can increase sputum viscosity, contributing to cystic fibrosis pathology.
• Nuclear actin-histone interactions may influence gene expression.