UC Irvine

Phosphorylation dependent regulation of GLI transcription factors and Hedgehog signaling

By

Eric TaraporeDoctor of Philosophy in the Biological Sciences University of California, Irvine, 2022 Associate Professor Scott Atwood, Chair

Basal cell carcinoma (BCC) is one of the most prevalent cancers and is mainly driven by the overactivation of the Hedgehog (HH) signaling pathway. Although easily treatable via Smoothened inhibitor vismodegib, drug resistance is common and as such alternative avenues to treat BCCs must be identified. One way to target pathway activity is through targeting the transcription factors responsible for relaying the signals. Here we use a combination of molecular biology techniques to identify additional ways to regulate the HH signaling pathway. We identify phosphorylation as being a key regulator of GLI activity and binding. We identify that AURKA plays a key role in regulating BCC growth in vitro and in vivo. We found that pharmacological inhibition of AURKA in the Ptch1fl/fl; Gli1-CreERT2 mouse BCC tumor model resulted in significantly reduced levels of BCC cell growth. Inhibition of AURKA in BCC cells in vitro resulted in reduced levels of HH signaling and cell growth. This goes with work that was conducted showing that phospho-mimetic mutation of the zinc finger domain of GLI results in differential levels of DNA binding and activity. We identify a specific region of the zinc finger domain that is permissive to phospho-mimetic mutation whereas other regions of the zinc finger completely abolish DNA binding and activity. We have termed these as the permissive regulatory region along with the more restrictive DNA binding region and linker region. Further studies into additional zinc finger transcription factors seem to show similar results although not to the same extent as GLI. Together these finding identify alternate means of GLI regulation, either through phosphorylation of GLI via AURKA or phosphorylation of the zinc finger binding domain of GLI.