Mouse Anti Human Topoisomerase I Hybridoma [DQUD-UPQ2-NU-4]

3-Nitroindenoisoquinoline human topoisomerase IB (Top1) poisons have potent antiproliferative effects on cancer cells. The undesirable nitro toxicophore could hypothetically be replaced by other functional groups that would retain the desired biological activities and minimize potential safety risks. Eleven series of indenoisoquinolines bearing 3-nitro bioisosteres were synthesized. The molecules were evaluated in the Top1-mediated DNA cleavage assay and in the National Cancer Institute's 60 cell line cytotoxicity assay. The data reveal that fluorine and chlorine may substitute for the 3-nitro group with minimal loss of Top1 poisoning activity. The new information gained from these efforts can be used to design novel indenoisoquinolines with improved safety.

The autoimmune regulator (AIRE) protein is the key factor in thymic negative selection of autoreactive T cells by promoting the ectopic expression of tissue-specific genes in the thymic medullary epithelium. Mutations in AIRE cause a monogenic autoimmune disease called autoimmune polyendocrinopathycandidiasis- ectodermal dystrophy. AIRE has been shown to promote DNA breaks via its interaction with topoisomerase 2 (TOP2). In this study, we investigated topoisomerase-induced DNA breaks and chromatin structural alterations in conjunction with AIRE-dependent gene expression. Using RNA sequencing, we found that inhibition of TOP2 religation activity by etoposide in AIRE-expressing cells had a synergistic effect on genes with low expression levels. AIRE-mediated transcription was not only enhanced by TOP2 inhibition but also by the TOP1 inhibitor camptothecin. The transcriptional activation was associated with structural rearrangements in chromatin, notably the accumulation of gamma H2AX and the exchange of histone H1 with HMGB1 at AIRE target gene promoters. In addition, we found the transcriptional up-regulation to co-occur with the chromatin structural changes within the genomic cluster of carcinoembryonic antigen-like cellular adhesion molecule genes. Overall, our results suggest that the presence of AIRE can trigger molecular events leading to an altered chromatin landscape and the enhanced transcription of low-expressed genes.