About the Project
Deanery of Biomedical Sciences
Currently, 112 different non-human papillomavirus (PV) types are known, which have been isolated from a broad range of 54 host species including cattle, canines, horses, rodents, bats, dolphins and primates. Bovine PVs (BPV) are associated with cancer, similar to the high risk types of the >100 different known Human Papillomaviruses (HPV). The diverse PVs possess a highly conserved genome structure, but only the core proteins E1, E2, L2 and L1 are present in all PV genomes characterized by now. Most PVs, however, encode 8 proteins. PVs that cause cancer encode several oncogenes which cause cellular transformation, including E7 which interacts and inhibits the tumor suppressor Retinoblastoma (pRb) protein1. pRb binds to and suppresses the transcription factor E2F which controls the expression of proteins involved in cell cycle control and cellular proliferation2. High risk E7 leads to destabilization and degradation of pRb via a LxCxE motif. In our previous work we found that the cellular protein SPZ1 interacts with E7 derived from high risk but not low risk HPV and binds adjacent to the LxCxE motif in E7. SPZ1 is a helix-loop-helix domain protein reported to be involved in MAP kinase signalling, transcriptional regulation and proliferation3. We found that SPZ1 is secreted via a non-classical secretion pathway and induces proliferation in human keratinocytes. If coexpressed with high risk E7, however, it inhibits E7-induced cellular proliferation of keratinocytes. In pulse-chase experiments with cycloheximide SPZ1 leads to an increased abundance of tumour suppressor pRb in E7 transformed cells, but also inhibits the degradation of E7. Thus, SPZ1 inhibits E7 by fixing and accumulating it in a non-functional form, and is able to either switch on or off cell cycle control depending on the cellular context.
In this Ph.D. project, we will further investigate how the secreted tumour suppressor protein SPZ1 inhibits cellular transformation, and whether recombinant soluble SPZ1 can be used to treat PV-caused cancers. In particular, we will test if SPZ1 acts via Rb, whether it affects the degradation pRB and thereby controls the cell cycle, whether SPZ1 forms a heterotrimeric complex with pRB and E7, whether other cellular proteins are involved and whether SPZ1 secretion via the non-classical pathway can be blocked or enhanced. Furthermore, we will also test whether SPZ1 is effective against other cancers in which pRB is mutated but which are not caused by PV E7. A broad range of different molecular, biochemical and cellular methods will be applied, including cutting edge technologies such as genome-wide RNAi screens and CRISPR/Cas9 gene editing.
References
1. Giarre M, Caldeira S, Malanchi I, Ciccolini F, Leao MJ, Tommasino M. Induction of pRb degradation by the human papillomavirus type 16 E7 protein is essential to efficiently overcome p16INK4a-imposed G1 cell cycle Arrest. Journal of virology 2001; 75(10): 4705-12.
2. Klingelhutz AJ, Roman A. Cellular transformation by human papillomaviruses: lessons learned by comparing high- and low-risk viruses. Virology 2012; 424(2): 77-98.
3. Hsu SH, Hsieh-Li HM, Huang HY, Huang PH, Li H. bHLH-zip transcription factor Spz1 mediates mitogen-activated protein kinase cell proliferation, transformation, and tumorigenesis. Cancer Res 2005; 65(10): 4041-50.
Funding Notes
This 4 year PhD project is part of a competition funded by EASTBIO BBSRC Doctoral Training Partnership. This opportunity is only open to UK nationals (or EU students who have been resident in the UK for 3+ years immediately prior to the programme start date) due to restrictions imposed by the funding body. EU applicants without a history of residency in the UK are eligible to apply, but would only be awarded the fees (not the stipend). All candidates should have or expect to have a minimum of an upper 2nd class degree in an appropriate discipline.
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