A cytosol protease from the estrogen-resistant C3H mammary carcinoma increases the affinity of the estrogen receptor for DNA in vitro.
We have previously shown, in the estrogen-unresponsive C3H mouse mammary tumor that the affinity of the estrogen receptor (ER) for calf thymus DNA in vitro is four-times higher than that of uterine ER [Baskevitch, P. P., Vignon, F., Bousquet, C. and Rochefort, H. (1983) Cancer Res. 43, 2290]. By mixing cytosols from this tumor and uterus, we describe a tumor factor capable of increasing ER affinity for DNA, as assayed by DNA-cellulose chromatography and saturation studies. The activity of this factor was inhibited by alpha-chymotrypsin-inhibitors such as N-tosylphenylalanylchloromethane and chymostatin. Using the fluorogenic substrate glutarylglycylglycylphenylalanyl-N-naphthylamide, we assayed such a protease in the C3H mammary tumor cytosol. This protease and the factor altering ER-DNA binding were eluted together from chromatography on DEAE-cellulose, AcA 44, and carboline-agarose and were sensitive to the same inhibitors. The partially purified factor decreases the molecular mass of the estrogen receptor as seen by denaturing electrophoresis after covalent labelling of the ER with [3H]tamoxifen aziridine. We suggest that the increase of ER affinity for DNA and the decrease of ER molecular size are due to the same protease with an alpha-chymotrypsin-like specificity.
D000818:Animals; D002417:Cattle; D002846:Chromatography, Affinity; D002918:Chymotrypsin / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology*; D004247:DNA / Q000378:metabolism*; D004351:Drug Resistance; D005260:Female; D066298:In Vitro Techniques; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology*; D051379:Mice; D008809:Mice, Inbred C3H; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000302:isolation & purification / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011960:Receptors, Estrogen / Q000378:metabolism*; D012756:Sheep; D014599:Uterus / Q000378:metabolism
D011960:Receptors, Estrogen; D004247:DNA; D010447:Peptide Hydrolases; D002918:Chymotrypsin