Nucleotide excision repair (NER) is an essential DNA damage repair pathway that removes bulky DNA lesions formed by exposure to ultraviolet light, environmental toxins, and platinum (Pt)-based chemotherapeutic drugs that are a standard of care for many cancer types. Mutation or decreased NER gene expression in cancer correlates with improved patient survival after Pt-based chemotherapy. However, the impact of most missense mutations in NER genes is unknown, and few approaches exist to reliably identify nonrecurrent passenger mutations with functional consequences. In this study, a multidisciplinary strategy will be developed to predict, validate, and characterize NER-defective mutations in the essential NER scaffold protein Xeroderma Pigmentosum Complementation Group A (XPA). Computational analyses were used to score NER-deficient versus NER-proficient mutations for further study. Predicted NER-deficient XPA mutants are being expressed in human XPA-deficient cells and screened for both NER activity and cisplatin sensitivity. In-depth biophysical and structural studies are being implemented to elucidate mechanisms of dysfunction. Identifying NER-deficient mutations that may sensitize tumors to Pt-based chemotherapies represents a promising strategy to stratify patients for optimal treatment strategies.