My previous research demonstrated that a SUMO-targeted ubiquitin ligase complex, Slx5/Slx8 (RNF4 in mammalian), supports cell survival despite the damaged genome in budding yeast (Saccharomyces cerevisiae). We reason that this finding in yeast can be translated to mammalian cells since the pathways involved in the process are functionally conserved. In fact, understanding the tolerance pathway for genome instability has a significant implication in cancer. Indeed, genome instability is one inherent characteristics of malignant cells. How cancer cells withstand the burden of unstable genome is poorly understood.
The experimental evidence led us to pursue RNF4 function in the tolerance of genome instability. We asked two research questions during this summer. First, do mutations of RNF4 identified in cancer tissues contribute to genome stability? Second, does RNF4 confer cancer cells resistance to replication stress?
For the first project, we took advantage of the functional conservation of RNF4 between Saccharomyces cerevisiae and human cells. We introduced wild-type RNF4 or mutant RNF4 carrying one of the cancer-associated mutations into yeast and tested their ability to grow in the presence of genotoxic chemicals.
For the second project, we examined if overexpression of RNF4 changes the response of cancer cells to replication stress. To this end, we used breast cancer cell lines and cell biology techniques to observe cells in mitosis or cells with micronuclei.