Identification of DNA topoisomerases induced by interleukin‐2 in HuT 78 cells

The activities of both type I and type II DNA topoisomerases are induced in three transient peaks in HuT 78 cells, a human T cell lymphoma cell line, within 12 hrs after treatment of the cells with 1,000 units interleukin‐2 (IL‐2)/ml [Pham et al ., Biochem. Biophys. Res. Comm. 390 (2009) 577–580]. The identities of the type I and type II DNA topoisomerases induced by IL‐2 were determined by immunoprecipitations of the enzymes from nuclear extracts of IL‐2‐treated HuT 78 cells using polyclonal antibodies specific for DNA topoisomerase I and DNA topoisomerase IIIα (type I enzymes) and for DNA topoisomerase IIα and DNA topoisomerase IIβ (type II enzymes). The immunoprecipitates were assayed for catalytic activities of DNA topoisomerase I and DNA topoisomerase IIIα by relaxation of supercoiled pBR322 DNA. The results indicate that DNA topoisomerase I, but not DNA topoisomerase IIIα, is activated in IL‐2‐treated HuT 78 cells. The immunoprecipitates were assayed for catalytic activities of DNA topoisomerase IIα and DNA topoisomerase IIβ by decatenation of kinetoplast DNA. The results indicate that both DNA topoisomerase IIα and DNA topoisomerase IIβ are activated upon treatment of HuT 78 cells with IL‐2. Therefore, the activities of DNA topoisomerase I, DNA topoisomerase IIα, and DNA topoisomerase IIβ are transiently activated in IL‐2‐treated HuT 78 cells. This work was supported by grants from the Morrison Trust and the NIH (HD 52388).