Nucleic Acids Research, 1987, Vol. 15, No. 20 8217-8234
© 1987
Articles |
Effects of the antitumor drug VP16 (etoposide) on the archaebacterial Halobacterium GRB 1.7kb plasmid in vivo
Laboratoire de Biologie Moléculaire de la Réplication ER 272, CNRS-IRSC, 7 rue Guy Môquet, BP No.8, 94802 Villejuif Cédex, France
Received July 28, 1987. Revised September 25, 1987. Accepted September 25, 1987.
The topoprofile of 1.7 kb plasmids from the archaebacterium Halobacterium GRB was analysed from cells growing with or without VP16 (etoposide). This drug interferes with the breakage-reunion reaction of eukaryotic DNA topoisomerase II by inhibiting the ligase activity of this enzyme.
Addition of VP16 to the culture medium of Halobacterium GRB cells results in the introduction of single- and double-strand DNA breaks in part of the plasmid population, with proteins covalently associated at their 5' ends. While some of the remaining covalently closed circular DNA molecules are relaxed, VPl6 treatment also gives rise to the production of positively supercoiled 1.7 kb plasmids. In contrast to adriamycin, VP16 does not intercalate into the 1.7 kb plasmid DNA in vivo. These results suggest that the VP16 target in halobacteria is a DNA topoisomerase II. Three major cleavage sites were detected on the 1.7 kb plasmid after VP16 treatment in vivo.