Magister Scientiae - MSc (Biotechnology)

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https://hdl.handle.net/10566/13204

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Browsing by Subject "15N-HSQC"

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    An investigation of the zinc binding characteristics of the RING finger domain from the human RBBP6 protein using heteronuclear NMR spectroscopy.
    (University of the Western Cape, 2007) Mulaudzi, Takalani; Pugh, David J.R.; Magister Scientiae - MSc; Faculty of Science
    Retinoblastoma binding prot ein 6 (RBBP6) is a 250 kDa human splicing-associated protein that is also known to interact with tumour suppresso r proteins p53 and pRb and to mediate ubiquitination of p53 via its intera ction with Hdm2. RBBP6 is highly up regulated in oesophageal cancer, and has been shown to be a promising target for immunotherapy against the disease. RBBP6 is also known to play a role in mRNA splicing, cell cycle control and apoptosis.
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    Structural characterisation of the interaction between RBBP6 and the multifunctional protein YB-l
    (University of the Western Cape, 2010) Muleya, Victor; Pugh, David J. R.
    Retinoblastoma binding protein 6 (RBBP6) is a 250 kDa RING finger-containing protein whose function is known to be mediated through interaction with other proteins. RBBP6 plays a role in the regulation of the tumour suppressor protein p53 and is also thought to be involved in mRNA splicing although its role has yet to be characterised. A recent study utilising a yeast 2-hybrid screen identified the cancer-associated protein known as YB-l as an interacting partner of RBBP6, and showed that RBBP6 ubiquitinates YB-I, leading to its degradation in the proteasome.Human Y-box binding protein 1 (YB-I) is member of the cold-shock domain family of proteins, which regulates a number of growth related genes through both transcriptional and translational mechanisms. YB-l is a cell-survival factor whose expression is increased in proliferating normal and cancer cells. It also protects cells against p53-mediated apoptosis by repressing the p53- promoter and down-regulating endogenous p53. The interaction between RBBP6 and YB-l involves the RING finger-like domain ofRBBP6 and the C-terminal62 amino acids ofYB-l. As a means of further localising the interaction, truncated fragments derived from the C-terminal region of YB-I, were tested for their interaction with the RING finger domain of RBBP6 using three different assays: a directed yeast 2-hybrid assay, co-immunoprecipitation and NMR chemical shift perturbation analysis. Our results suggest that the entire 62 amino acid region at the C-terminal domain ofYB-l may be involved in the interaction with RBBP6. Using chemical shift perturbation analysis, this study provides an indication of where YB-l binds to the RING fmger. This represents the first step towards the design of therapeutics aimed at modulating the interaction between RBBP6 and YB-l as a means of targeting the oncogenic effects ofYB-l. In order to identify E2 enzymes involved in the ubiquitination of YB-I, we examined the efficiencies of selected E2s in an in vitro ubiquitination assay. UbcH5c and UbcH7 were both found to catalyse the ubiquitination of YB-l in conjuction with RBBP6, whereas Ubc 13 was not. Finally, we show using NMR that two single-point mutations of the RING finger-like domain are sufficient to abolish homodimerisation of the domain. These will be used in future studies to investigate the requirement for homodimerisation on the ubiquitination activity of RBBP6. www.etd.