Epigenetics

There has been substantial progress in cancer research that has markedly enhanced patient outcomes. However, chemotherapy resistance persists and often leads to multidrug resistance, rendering cancer cells unresponsive to multiple chemotherapy drugs, presenting a significant challenge in the effective treatment of the disease. Dysregulation in gene expression patterns caused by abnormalities in epigenetic mechanisms have been identified as contributing factors to the development and progression of cancer. Epigenetic research offers potential to discover drugs that target specific epigenetic modifications to regulate gene expression patterns in the context of chemotherapy resistance. I hypothesize that histone modifications on histone H3 and histone H4 contribute to doxorubicin resistance. The data presented here provides an initial screening of the mutant monoallelic histone yeast strains to identify post-translationally modifiable amino acids in H3 and H4 that could contribute to doxorubicin resistance. The possible targets of histone modifications were then repeated in triplicate to obtain statistical significance. Finally, Western blot techniques were used to identify the modification occurring on the histone H3 and histone H4 amino acid sites that were previously identified to be statistically significant.

Epigenetic dysregulation has been implicated in oncogenesis, with post-translational histone modifications being linked to cancer progression. WSTF/BAZ1B forms chromatin-remodeling complexes with other proteins and lowers cancer survival outcomes. Treatment resistance causes >90 % of all cancer deaths. In particular, cancers develop tolerance to cisplatin-induced genotoxicity. It is hypothesized that the BAZ1B bromodomain, PHD finger, and DDT domain recognize epigenetic modifications, contributing to cisplatin resistance in cancers. To test this, the domains were expressed in Rosetta 2 BL21(DE3) and Rosetta 2 BL21(DE3) PLysS Escherichia coli strains. Soluble proteins were extracted, purified, and then analyzed using pulldown assays and modified histone peptide arrays. The DDT and PHD finger domains were found to bind to specific histone modifications with the DDT domain also displayed DNA-binding properties. Some of the identified histone modifications have known roles/correlations in normal and cancer cells, implicating BAZ1B as an agent in oncogenesis, treatment resistance, and as a therapeutic target.