Ishibe Y, Klinge C M, Hilf R, Bambara R A
Department of Biochemistry, University of Rochester, School of Medicine and Dentistry, New York 14642.
Biochem Biophys Res Commun. 1991 Apr 15;176(1):486-91. doi: 10.1016/0006-291x(91)90950-c.
We have recently used DNA containing estrogen responsive element (ERE) sequences for affinity purification to prepare calf uterine estrogen receptor (ER) at near homogeneity. The capacity of this purified ER to alter DNA topology upon binding was examined. Although the ER is not a topoisomerase, the presence of ER changes the distribution of topoisomers generated by incubation of plasmid DNA with excess wheat germ topoisomerase I. This effect is larger in plasmids containing a consensus ERE sequence. Two dimensional gel electrophoretic analysis suggested that interaction of ER and ERE causes negative supercoiling in regions of the plasmid accessible to topoisomerase I, resulting from overwinding of DNA contacting the ER. The extent of topological alteration was dependent on ER concentration. We suggest that the observed conformational changes in the DNA could have a role in regulation of transcription.
