OMICs based identification of the mechanisms that underpin FAK’s regulation of gene expression
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Date
27/06/2020Author
Griffith, Billie Georgina Cooper
Metadata
Abstract
Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase, commonly overexpressed
in cancer that is well known to be a key regulator of cancer cell proliferation,
survival, migration and invasion. It has recently been shown to modulate the antitumour
immune response via transcriptional regulation of chemokines and cytokines.
These findings have fuelled interest in FAK as a plausible therapeutic target in cancer
and FAK kinase inhibitors are currently in Phase I and II clinical trials.
To date, much of the research on FAK has focused on its role at focal adhesions,
detailing its major functions in cell motility and cancer cell invasion. However, 16
years ago, FAK was shown to translocate to the nucleus and it is now well established
that this occurs under conditions of cellular stress such as oncogenic transformation.
In the nucleus, FAK binds to a number of transcription factors such as P53, MDM2,
IL33, RUNX1 and SP1. These nuclear interactions have been linked to proliferation,
survival, differentiation and regulation of the anti-tumour immune response and cell
cycle. However, despite these findings, the mechanism by which FAK regulates gene
expression in the nucleus has yet to be defined. With FAK kinase inhibitors currently
in clinical trials, it is important to understand the molecular mechanisms associated
with FAK’s transcriptional regulation, the role of the kinase activity, and the potential
therapeutic benefits of targeting FAK’s nuclear function.
We therefore investigated the mechanism by which FAK regulates transcription by
integration of a number of ‘omics’ approaches to define the nuclear FAK interactome
and FAK-dependent gene programmes, as well as FAK’s role in regulating chromatin
accessibility and transcription factor binding. Integration of these datasets predicted
that FAK regulates the binding of AP-1 and ETS transcription factors to chromatin.
Furthermore, our findings indicate that a subset of FAK-regulated genes display
changes in chromatin accessibility. Chromatin ImmunoPrecipitation (ChIP) validation
experiments on the enhancer region of one of these genes, IL33, show reduced binding
of JUN upon loss of FAK’s kinase activity. This predicts that FAK is regulating
chromatin accessibility at this region of the IL33 gene.
The work presented in this thesis therefore identifies a novel mechanism by which
FAK regulates transcription; further experiments will be required to define the
epigenetic complexes responsible for FAK-dependent chromatin accessibility
changes. This work adds to our understanding of how an integrin adhesion protein can
control cancer cell behaviour via transcription in the nucleus.