The Effect Post-Translational Modifications on p53 Stability and Function

p53 is a transcription factor often disregulated in cancer. Its activation occurs in response to DNA damage and induces the expression of genes involved in the cell cycle, metabolism, apoptosis and senescence. Its activity is modulated by a wide range of post-translational modifications such as phosphorylation, acetylation, ubiquitinylation and conjugation of ubiquitin-like proteins such as Nedd8 (Neddylation) and ISG15 (ISGylation). The effect of ISGylation on p53 varies between degradation (especially in the case of misfolded p53) via the 20S proteosome and an increase in transcriptional activity. Conjugation of ISG15 occurs via an E3 ligase (HERC5 and/or EFP), and the interaction between p53 and these E3 ligases has been shown to be promoted by p53 phosphorylation at Y126 and Y220 by Src; these two phosphorylation sites are also common points of mutation in cancer. My research will focus on the effect of ISGylation on p53. To that end, I aim to first express p53 phosphorylated at Y126 and/or Y220 using amber stop codon suppression to probe the impact of phosphorylation at these sites on p53 stability and ISGylation. Because there is very little literature on ISGylation and p53, I am also preparing a backup project focusing on p53 acetylation.