Date of Award
Doctor of Philosophy (PhD)
The tumor suppressor protein p53 transactivates genes involved in cell cycle arrest and apoptosis in response to DNA damage, cellular stress and some oncogenic proteins. The wild type polypeptide chain of p53 has four distinct domains, including the sequence specific DNA binding core domain and the C terminal tetramerization domain. p53 must retain its ability to oligomerize and bind DNA targets in vivo to fulfill its function. Using X-ray crystallography and a crosslinking strategy, the structure of a wild type tetrameric p53 core domain bound to its consensus sequence was solved. This structure gives insight into DNA bend, core domain-DNA binding cooperativity and surface residue conservation within the tetramer.
Many cancers result from cells harboring mutant forms of p53 that are unable to function due to their inability to oligomerize, DNA binding defects or, in the case of human papillomavirus infection, p53 degradation.
High risk forms of the human papillomvirus (HPV) infect the basal layers of stratified epithelia and express two oncoproteins, called E6 and E7, which can lead to cell cycle disruption and cervical cancer. E6 mediates its cell transformation, in part, by forming a complex with the cellular E3 ligase E6-Association Protein (E6AP) to target p53 for degradation by the ubiquitin- viii proteasome pathway. A high throughput solution screen was designed to search for small molecule inhibitors of the E6 / E6AP interaction. Of the 80,000 compounds that were screened, 30 inhibitors with IC50 values in the low-micromolar to mid-nanomolar range were confirmed using secondary assays. Two compounds were shown to specifically block p53 degradation and promote apootosis in cell lines infected with high risk forms of HPV. These HPV-E6 inhibitors provide a framework for developing HPV inhibitors with possible therapeutic applications.
Malecka, Kimberly A., "The tumor suppressor protein p53 and the antagonizing oncoprotein E6 from human papillomavirus type 16" (2010). Publicly Accessible Penn Dissertations. Paper 277.