Assessing histone H2A.Z and the H2A tails in chromatin structure
Date
2018
Authors
Seidel, Erik, author
Hansen, Jeffrey, advisor
Stargell, Laurie, committee member
Bailey, Susan, committee member
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Abstract
Deoxyribose nucleic acid (DNA) is a negatively charged macromolecule that encodes life's genetic material. In organisms, it is bound to net positively charged histone proteins in specific fashions and then compacts with magnesium and calcium to form domains and then chromosomes, which occupy territories in the nucleus during interphase. The mechanism of this compaction has been debated and studied for decades, and the employment of specific protein structures in molding chromatin morphology is still under review. This thesis adds to this story by testing how higher order chromatin structure is influenced by a histone H2A variant, H2A.Z, and the combined effect that the so-called histone H2A N and C terminal tails, when contrasted to arrays involving wildtype canonical H2A. An in vitro model system of nucleosomal arrays consisting of sea urchin derived 5S ribosomal DNA and recombinant mammalian histone proteins was used. Both the H2A.Z and H2A tailless arrays required increased magnesium to oligomerize into possibly domain-like structures. The H2A.Z protein produced similarly accessible structures as the fully accessible wildtype control as learned through a micrococcal nuclease digestion method designed for these chromatin structures. The deletion of the H2A N and C terminal tails produced oligomers with slightly less accessible linker DNA than its wildtype control according to the micrococcal nuclease digestion. Furthermore, the H2A.Z, H2A double tailless, and H2A wildtype oligomers were globular in shape. When subjected to fluorescence recovery after photobleaching (FRAP), the oligomers involving H2A.Z agreed with the current literature describing its presence in euchromatin and heterochromatin, and its mobility correlated with that of a more mobile and possibly more open structural agent. Taken together, the H2A and H2A.Z proteins are influential in determining and providing variability to the overall chromatin structure that is vital to DNA's role in biology.
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Subject
H2A C-terminal tail
H2A.Z
chromatin
micrococcal nuclease
H2A N-terminal tail