Stability of DNA in nucleosomes

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Chromatin core particles are fundamental units of DNA packaging in eukaryotes.
• Histones within chromatin undergo thermal denaturation, influencing DNA stability.
• Understanding the thermodynamic contributions of protein and DNA to chromatin stability is crucial.

Purpose of the Study:

• To quantify the heats of thermal denaturation for chromatin core particles.
• To investigate the effect of covalently crosslinked histones on chromatin stability.
• To determine the enthalpy change for DNA denaturation within core particles.

Main Methods:

• Differential scanning calorimetry (DSC) was employed to measure thermal denaturation.
• Chromatin core particles with and without crosslinked histones were analyzed.
• High-salt solutions were used to isolate protein denaturation contributions.

Main Results:

• The additional stabilization from histone crosslinking was not reflected in transition enthalpy.
• Protein denaturation contributed to the overall heat measured by DSC.
• The enthalpy change for DNA denaturation in core particles is comparable to naked DNA.

Conclusions:

• Histone crosslinking does not significantly alter the DNA denaturation enthalpy in chromatin core particles.
• The thermodynamic stability of DNA within the chromatin core particle is similar to free DNA.
• Protein denaturation contributes to the overall thermal transition but does not change the DNA denaturation enthalpy significantly.