Nucleic Acids Research, 1988, Vol. 16, No. 10 4705-4720
© 1988
Articles |
A twenty-two-fold increase in the relative affinity of estrogen receptor to poly (dA-dC).poly (dG-dT) in the presence of polyamines
Division of Medical Oncology, Department of Medicine, Box 168, University of Minnesota Hospital and Clinic, University of Minnesota Minneapolis, MN 55455, USA
*Author to whom all correspondence should be addressed (Box 168 UMHC).
Received November 12, 1987. Revised March 9, 1988. Accepted March 9, 1988.
We studied the relative efficacy of polyamines to facilitate the binding of estrogen receptor to poly (dA-dC).poly(dG-dT). In the absence of polyamines, 1,400 µg/ml of this polynucleotide eluted 50% of bound estrogen receptor from DNA-cellulose. In contrast, 50% estrogen receptor was eluted by 65 µml of poly(dA-dC).poly(dG-dT) complexed with 150 µM spermidine. Putrescine and spermine also enhanced the ability of poly(dA-dC).poly(dG-dT) to elute estrogen receptor, but the magnitude of the effect was not as high as that of spermidine. Control experiments with calf thymus DNA and poly(dA-dT).poly(dA-dT) showed 6- and 3-fold increase, respectively in their affinity for estrogen receptor in the presence of spermidine. The dramatic increase in the affinity of poly(dA-dC).poly(dG-dT) for estrogen receptor in the presence of polyamines might be a result of the conversion of the polynucleotide to the left-handed Z-DNA form. These results show that polyamines are capable of participating in estrogenic regulation of gene expression by altering the affinity of the receptor for specific DNA sequences.