Helen Walden

Structural and functional studies of the Parc-p53 interaction

The ubiquitin-proteasome pathway (UPP) has emerged as a predominant cellular regulatory mechanism with roles in controlling cell-division, signal transduction, development and the immune response. It is also implicated in many neurodegenerative diseases, since cellular aggregates characterising neurodegeneration are heavily ubiquitinated. Mutations in p53 are linked to more than 50% of human cancers, making it an important protein in the understanding of cancer and cell biology.

p53 acts as a transcription factor and tumour suppressor. It was recently demonstrated that Parc (p53-associated Parkin-like cytoplasmic protein), a protein overexpressed in some neuroblastoma cell lines, anchors wild-type p53 in the cytoplasm, preventing its translocation to the nucleus and exerting its transcriptional and tumour suppressor roles. Structural characterisation of the interactions between Parc and p53 is necessary to understand how Parc retains p53 in the cytoplasm and how to disrupt this sequestration.

Parc encompasses two domains linked to the ubiquitin-conjugating cascade. One shares significant sequence homology with Cullin-7, an E3-ubiquitin-ligase, and the second resembles Parkin, another E3-ubiquitin-ligase, mutations in which are linked with an early-onset familial form of Parkinson's Disease.

As a structural biology lab, we would like to understand the molecular basis for the reported interaction between Parc and p53 with an eventual aim of disrupting that interaction. The PhD project would entail expressing the purported interacting fragments of Parc and p53, developing a functional assay for this interaction so that mutants can be constructed to test for functional residues.

The overall aims of the project will be to structurally define and biochemically characterise the interaction between Parc and p53.