Nucleosome is the basic repeating unit of the eukaryotic chromatin. It is composed of 146 bp DNA and a histone octamer, which consists of a (H3-H4)2 tetramer and two H2A-H2B dimers. Crystal structure shows that 146 bp DNA wraps around the histone octamer and makes a ~1.7 negative superhelix turn. Packaging of DNA within nucleosome introduces energetic barrier for DNA-related process, such as genome expression, replication and repair. In order to retrieve the encoded information, DNA must be at least partially unwrapped to allow the access by DNA binding proteins to perform their functions. Therefore, in order to understand the accessibility of DNA within the nucleosome, it is important to understand the nucleosome disassembling process and the accompanying energetics. In this work, we use differential scanning calorimetry to characterize the nucleosome and also its subunits. We want to examine how the thermal and thermodynamic stabilities of either DNA or the histone proteins are changed when incorporated into the nucleosome. We are also interested in the steps that are involved in the nucleosome disassembling process. The obtained results may contribute to the understanding of energetic requirement for DNA-related processes.

Calorimetric study of nucleosome

247th National Meeting (2014)

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