Rad23 is a protein involved in both nucleotide excision repair (NER) and proteasome-mediated degradation, and has been suggested to facilitate interactions between these two pathways. Until recently, Rad23-related research has been conducted using Saccharomyces cerevisiae. By instead using Tetrahymena thermophila, which has a transcriptionally silent micronucleus, the role of Rad23 in global genome NER (ggNER) can be better understood. The T. thermophila homolog for RAD23 was identified through bioinformatics analysis. Expression levels and ubiquitination of Rad23 before and after multiple genotoxic stressors was assessed using qRT-PCR and western blot analysis, respectively. Additionally, interacting partners of Rad23 in both the proteasome and the NER pathway will be analyzed using fluorescent co-localization and co-immunoprecipitation. Finally, survival assays of knockdown strains will be used to determine the roles of Rad23 and other interacting partners. An advantage of this research is that tagging and knockdown constructs will be created by using an endogenous tagging vector. Inserting a tagged gene into its natural locus under its own promoter prevents aberrant expression and phenotypes from an inducible promoter that can result from certain experimental conditions. .