Requirement of DNA topoisomerases for in vitro chromatin assembly by 3T6 mouse cell extracts.
Nuclear extracts of 3T6 mouse cells were able to assemble in vitro minichromosomes which displayed a 150-bp periodicity. Activities of both DNA topoisomerases I and II were detected in these extracts. When a supercoiled pUC DNA was added, it was first relaxed in less than 3 min, then slowly supercoiled again in 1-4 h. Both reactions occurred either in the absence or the presence of added Mg2+ and/or ATP, they were not blocked by DNA topoisomerase II inhibitors and they were inhibited by an antiserum against DNA topoisomerase I and by camptothecin. These findings led us to propose that, under our in vitro assay conditions, chromatin assembly is mainly carried out by a DNA topoisomerase I.
Cáceres
J F
JF
Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Universidad de Buenos Aires, Argentina.
Blangy
D
D
Glikin
G C
GC
D000818:Animals; D002478:Cells, Cultured; D002843:Chromatin / Q000378:metabolism*; D004247:DNA / Q000302:isolation & purification / Q000378:metabolism; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism; D007700:Kinetics; D051379:Mice
D002843:Chromatin; D004278:DNA, Superhelical; D004247:DNA; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II