| Summary: | <p>Mammalian genomes are characterised by unique regions of non-methylated DNA known as CpG islands (CGIs). These genomic elements are characterised by a high density of CpGs and an elevated GC content compared to the surrounding, bulk of the genome. CGIs are prevalently associated with the 5’ end of genes and represent key nucleation sites where specific transcription factors and chromatin modifiers are recruited to impact on gene function. </p> <p>This thesis is focused at understanding the biochemical properties of the recently discovered H3K36-specific histone demethylase, KDM2A. This enzyme is specifically recruited to CGIs but how it interfaces with local chromatin <em>in vivo </em>remains unknown. Using defined chromatin templates in vitro, this study demonstrates that KDM2A binding to DNA relies on a zinc finger CXXC domain that preferentially recognizes non-methylated CpGs. In particular, nucleosomes represent a major barrier to KDM2A binding and chromatin substrates are interpreted by the CXXC domain through specific interaction with CpGs within linker DNAs. Moreover, the adjacent PHD domain does not contribute to KDM2A binding to chromatin.</p> <p>Together these observations suggest that sequence, methylation status and accessibility of DNA define how CGI chromatin is interpreted by CXXC domain proteins. In particular, the precise targeting of KDM2A to CGIs contributes to the creation of a unique chromatin architecture that highlights gene regulatory regions within large and complex mammalian genomes.</p>
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