| Summary: | <p>Enhancers are cis-regulatory DNA elements that bind transcription factors and drive
expression of target genes in a spatio-temporal manner. Despite their collective importance
in cell fate specification, up to now enhancers have often been studied in assays that ignore
the chromosomal context required for their function in vivo. In my DPhil, I aim to probe a
single enhancer sequence in situ, using the strongest enhancer at the mouse α-globin locus
as a model. The project addresses four main issues. Firstly, I test the sufficiency of a single
element (R2) to activate gene expression when removed from its super-enhancer context.
Impaired activation of the α-globin genes in this model highlights the importance of
sequence context in enhancer function. Secondly, I describe the characterisation of an in
vitro erythroid differentiation system to enable the analysis of novel genetic mutants of the
α-globin locus. Thirdly, I present in vitro data from a number of informative enhancer
combinations of the α-globin super-enhancer. Results support findings from the in vivo
single-enhancer model and highlight a potential role for seemingly inactive elements in
super-enhancer function. Finally, I zoom in from the level of a complete gene locus to that
of a single 238 bp transcription factor binding platform at the core of the R2 enhancer, to
determine the rules governing enhancer function at the sequence level. Ultimately, I aim to
determine which of the models of transcription factor binding and element co-operation are
most fitting at this locus and probe the principles of transcriptional activation.</p>
|
|---|