DNP-enhanced solid-state NMR spectroscopy of chromatin polymers

Area of Science:

• Biochemistry and Molecular Biology
• Structural Biology
• Genomics

Background:

• Chromatin, the genome's functional form, is a DNA-protein polymer organized into nucleosomes.
• Nucleosome structure involves DNA wrapped around histone proteins (H2A, H2B, H3, H4).
• Magic Angle Spinning (MAS) NMR spectroscopy offers high-resolution insights into nucleosomes but faces challenges like low sensitivity and complex interactions.

Purpose of the Study:

• To enhance the sensitivity and efficiency of MAS NMR for studying nucleosome arrays.
• To investigate the effects of low temperature on NMR spectral properties of chromatin.
• To capture functionally relevant protein-DNA and histone-histone interactions within chromatin.

Main Methods:

• Utilized dynamic nuclear polarization (DNP) to boost sensitivity in MAS NMR experiments on nucleosome arrays at 100 K.
• Evaluated temperature-dependent changes in chemical shifts and linewidths.
• Compared NMR spectra of chromatin samples with and without DNA to analyze histone-DNA interfaces.

Main Results:

• Achieved well-resolved 13C-13C MAS NMR correlations efficiently at 100 K.
• Observed minimal temperature-dependent spectral changes, primarily at histone-DNA and histone-histone contact sites.
• Detected chemical shift changes and line broadening at the DNA-histone interface using 13C-13C correlations.
• Demonstrated DNP's utility in detecting long-range histone-DNA correlations despite challenges with 15N-13C histone-histone interactions.

Conclusions:

• DNP-enhanced MAS NMR spectroscopy provides high resolution and sensitivity for chromatin analysis.
• The method effectively captures functionally relevant protein-DNA interactions.
• This technique has significant implications for understanding gene regulation and genome organization.