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Histone-histone interaction mediates chromatin unfolding at physiological ionic strength
1Department of Biochemistry, University of Nevada, Reno 89557.
Biochemistry
|July 11, 1989
Summary
Novel polyacrylamide sols stabilize chromatin, revealing DNA helix destabilization at physiological salt levels. This suggests histone interactions influence DNA conformation in vivo.
Area of Science:
- Biophysics
- Molecular Biology
- Genetics
Background:
- Chromatin structure and stability are crucial for DNA accessibility and function.
- Understanding chromatin behavior across physiological salt concentrations is essential.
Purpose of the Study:
- To investigate the thermal denaturation of chicken erythrocyte chromatin.
- To explore the stabilizing effects of critical-point polyacrylamide sols on chromatin.
- To elucidate DNA conformational changes in chromatin at physiological ionic strengths.
Main Methods:
- High-resolution thermal denaturation analysis of chromatin.
- Utilizing critical-point polyacrylamide sols as stabilizing solvents.
- Varying NaCl concentrations from low mM to high concentrations (4 orders of magnitude).
Main Results:
- Polyacrylamide sols effectively stabilized chromatin against precipitation at high salt concentrations.
- Low salt concentrations (<10 mM) showed slight chromatin destabilization at the nucleosome level, potentially due to histone-polyacrylamide interactions.
- Stabilization of pure DNA against denaturation by polyacrylamide at low salt concentrations was observed.
- Prominent low-temperature thermal transitions associated with DNA conformational changes were detected at and above 100 mM NaCl.
Conclusions:
- Histone-histone interactions at physiological ionic strengths (approx. 100 mM Na+) may be comparable to histone-DNA interactions.
- These interactions can destabilize the DNA helix within chromatin under physiological conditions.
- A model for local chromatin decondensation under physiological conditions is proposed.