Nature uses a special class of histone proteins, histone variants, to modulate the properties of chromatin at defined genomic locations. H2A.B is one of the most divergent H2A variants and is... Show moreNature uses a special class of histone proteins, histone variants, to modulate the properties of chromatin at defined genomic locations. H2A.B is one of the most divergent H2A variants and is involved in important cellular functions, such as transcription and mRNA splicing. Incorporation of H2A.B in nucleosomes causes unwrapping of ~15 bp entry/ exit nucleosomal DNA from the histone octamer core. Yet, the molecular basis of such peculiar nucleosome conformation is unclear. The work described in this thesis aimed to determine the impact of H2A.B incorporation on the structural and dynamical properties of the nucleosome, primarily using nuclear magnetic resonance (NMR) spectroscopy. Show less
Repair of damage in the DNA is essential for an organism. Therefore, several repair mechanisms have evolved. In this thesis, the mechanism of Transcription-Coupled Nucleotide Excision Repair (TC... Show moreRepair of damage in the DNA is essential for an organism. Therefore, several repair mechanisms have evolved. In this thesis, the mechanism of Transcription-Coupled Nucleotide Excision Repair (TC-NER) and the UV Damage Endonuclease repair pathway (UVDE) have been studied. Central to TC-NER is the protein Cockayne Syndrome protein A (CSA). Its biological importance can be seen in that mutations in CSA cause the human, serious disorder Cockayne Syndrome. This thesis describes structural and biochemical studies of this protein, which give insights into its substrate-binding and into how mutations in this protein cause the disease Cockayne Syndrome. Biochemical and structural studies of UVDE show the identity and role of its post-translational modification, a carboxylation. A cocrystal structure of UVDE with 6-4PP DNA shows how UVDE can recognize UV damaged DNA. Show less
