EXPRESSION OF THE TYPE-L DNA TOPOISOMERASE GENE IN ADENOVIRUS-5 INFECTED HUMAN-CELLS

The amount of topoisomerase I specific mRNA increases three- to fivefold during the early phase of infection of HeLa cells with adenovirus-5. The observed increase in specific mRNA is mainly due to an Increased rate of transcription of the gene. In human 293 cells, which constitutiveiy express the viral E1A and E1B genes, we determined an elevated level of topoisomerase I mRNA, comparable to the amount of mRNA present in HeLa cells early after infection with adenovirus. in contrats, in HeLa cells Infected with adenovirus d1312, a mutant were the E1A region had been deleted, the amount of topoisomerase I mRNA remained constant, unless the cells we superinfected with wild type virus. Our experiments indicate that the topolsomerase I gene is transactlvated by an early adenovirus protein product coded by the E1A region. in contrast to the increase In mRNA synthesis, the amount of topolsomerase I protein and the topoismerase I activity remain constant up to 24 hours after infection. © 1990 Oxford University Press.