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Title: DNA and chromatin binding sites on the globular domain of histone H5
Author: Duggan, Margaret Mary
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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Determination of the exact nature of the interaction between the linker histone H1 (and its variants such as H5 in mature chicken erythrocytes) and the nucleosome is essential to understand H1's role as a structural component of the nucleosome and higher-order chromatin structure, and its proposed roles in general and gene-specific transcriptional regulation (Chapter 1). Two DNA-binding sites on the globular domain of histone H5 (GH5) have been proposed, both of which have been implicated in binding to mixed-sequence ("bulk") nucleosomes. However, studies of a nucleosome assembled on DAN containing the Xenopus borealis somatic 5S rRNA gene have argued against a requirement for a second DNA binding site on GH5, raising the possibility that this nucleosome, and possibly others, bind linker histones differently from bulk nucleosomes, providing a basis for gene-specific effects of H1. The role of the proposed second site in binding to mixed sequence nucleosomes has been further investigated (Chapter 2). As a precursor to assessing the contribution of individual residues at site II, a GH5 mutant in which all four basic residues at this site were replaced with alanine was tested for its ability to bind mixed sequence nucleosomes and four-way junction DNA. The mutant was not able to stabilise a chromatosome, being unable to protect 166 bp of chromatosomal DNA from nuclease digestion. The ability to recognise four-way junction DNA was also abolished in the site II mutant. Single-residue mutants retained the ability to stabilise a chromatosome and to recognise four-way junction DNA, although subtle differences in binding were observed, supporting the idea that the second DNA-binding site consists of a cluster of positive charges.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available