Analysis of bacterial proteins interfering with eukaryotic cell proliferation

Descriptions of a role of some bacterial pathogens in counteracting tumour progression in humans date back to the end of XIX century. Recently, it was reported that two members of the family of cupredoxins, azurin from P. aeruginosa and rusticyanin from A. ferrooxidans, are able to enter in and to induce apoptosis and/or cell cycle arrest in a number of different cancer cell-lines. The apoptotic effect mediated by azurin was confirmed also in vivo. One of the specific aims of this thesis was to assess whether the expression of cupredoxins in S. cerevisiae could recapitulate the effects observed in mammalian cancer cell-lines. The induction of cupredoxins expression in yeast caused a strong growth delay accompanied by high cytotoxicity and alterations in cellular morphologies and bud emergence. These findings validated S. cerevisiae as a system to screen the plethora of bacterial proteins with potential anti-tumoral activity. Since, at least in the case of azurin, the pro-apoptotic effects on cancer cells was traced to direct interaction with the tumor suppressor protein p53, we also investigated the possibility to find new bacterial-derived interactors of p53 through Yeast Two Hybrid System. During this screening we observed the strong interaction of a bacterial protein with murine and human p53. This interaction was extremely specific as P. aeruginosa and E. coli homologs did not exhibit a similar behaviour.