Nucleosome structure and conformational states
The study of chromatin and nucleosomes by biochemical and biophysical methods is described. The techniques used include circular dichroism, thermal denaturation, analytical ultracentrifugation, nuclease digestion pattern, and electron microscopy. The effect of urea on the structure of nucleosomes and chromatin was studied. It was found that there are two domains in the nucleosome which respond differently to urea. The observation that different domains of the nucleosome exhibited different responses to urea offers a basis for viewing the altered conformation of transcriptionally active chromatin. Modulations of the DNA-rich shell by nonhistone proteins or histone modifications might occur with only minor alterations in the conformation of the protein-rich core, permitting rapid renaturation to the transcriptionally inactive chromatin configuration. In order to study the effect of DNA sequence and base composition on nucleosomal strcture, histone-DNA complexes containing histones (H2A, H2B, H3, H4) and a variety of DNAs, including synthetics, were reconstructed. The properties of the reconstructed complexes were similar to those of H1- and H5-depleted chromatin. Monomer nucleosomes were homogeneous with respect to DNA length and exhibited clear nucleosomal structure. It was possible to obtain good reconstruction between chicken erythrocyte inner histones and DNA of a wide variety of G + C%.Nucleosomes containing poly(dA-dT) gave detailed information about the internal structure of nucleosomes. The nucleosome appeared to have two domains of DNA differing in secondary structure. Nucleosomes containing poly(dA-dT) were also sensitive indicators of conformation changes in structure due to temperature and ionic strength.
- Research Organization:
- Univ. of Tennessee, Knoxville, TN (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- EY-76-C-05-0033
- OSTI ID:
- 5616930
- Report Number(s):
- DOE/TIC-10285
- Resource Relation:
- Other Information: Thesis
- Country of Publication:
- United States
- Language:
- English
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