Understanding the interactions of Aurora A kinase and its intrinsically disordered binding partners

Aurora A kinase (AurA) is a serine/threonine kinase essential for mitosis. AurA is
frequently overexpressed in cancers and is implicated in cancer-associated cellular
phenotypes such as centrosome amplification, aneuploidy, and mitotic checkpoint
override, making it a promising therapeutic target. Localisation and activation of
AurA depends on its binding partners, each associated with one of its various
functions, though few have been studied in detail. This work has focused on,
GADD45α and hnRNPK, two less well characterised interactions of AurA.
Growth Arrest and DNA Damage alpha protein (GADD45α) has been reported to
inhibit AurA kinase activity but the molecular basis remains unclear. In this work,
each GADD45 paralogue has been shown to interact with AurA and activate
autophosphorylation, contrary to previous observations. The binding interface
involves the C-terminus of GADD45α and in AurA, the TACC3 pocket on the N-
lobe and an adjacent putative α-helix.
Heterogenous nuclear ribonucleoprotein K (hnRNPK) is a substrate of AurA, and
their interaction is implicated in driving MYC transcription and promoting cancer cell
migration. In this work, hnRNPK has been shown to activate AurA kinase activity.
The interaction involves the TPX2 pocket on the N-lobe of AurA and an intrinsically
disordered region of hnRNPK that includes key residues Phe339 and Trp345. A
model of the complex is presented that is consistent with experimental data.
Previously characterised AurA binding partners are IDRs which fold upon binding to
AurA. Using TPX2 and AurA as a model, this project investigates the dynamics and
structural basis of folding-upon-binding in IDRs. Single α-helical domains were
fused to the C-terminus of the AurA-binding region of TPX2 to preform the α-helix
that otherwise folds upon binding to AurA. These modified constructs activate the
kinase and preliminary results suggest that their affinity for AurA is enhanced due to
an energetically more favourable interaction.