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Influence of Limited Proteolysis on the Physicochemical and DNA-binding Properties of Glucocorticoid Receptors from Corticoid-sensitive and -resistant Mouse Lymphoma P1798¹

Research Institute, Joint Diseases North General Hospital, Mount Sinai School of Medicine, New York, New York 10035

We have compared the DNA-cellulose-binding properties of cytosolic [³H]triamcinolone acetonide ([³H]TA)-receptor complexes from the corticoid-sensitive (CS) and corticoid-resistant (CR) strains of mouse lymphoma P1798. About 50% of heat-activated 61-Å (Stokes radius) CS complexes and close to 60% of heat-activated 28-Å (Stokes radius) CR complexes bound to DNA-cellulose. [³H]TA complexes from the CR lymphocytes were more refractory to extraction from DNA-cellulose with MgCl₂, spermidine, and KCl than were complexes from the CS cells. This behavior closely mimics the type of interaction previously observed after nuclear binding of [³H]TA in intact P1798 cells at 37°.

Limited digestion (30 min at 10°) of the 61-Å CS P1798 [³H]TA complex with chymotrypsin converted it to a 28-Å form in which interaction with DNA-cellulose (i.e., extractability with MgCl₂, spermidine, and KCl) was indistinguishable from the interaction with DNA-cellulose of undigested 28-Å CR P1798 [³H]TA-receptor complexes. Chymotrypsin treatment (30 min; 10°) of [³H]TA complexes from CR lymphocytes did not alter their Stokes radius or their extractability from DNA-cellulose. Proteolysis (30 min; 10°) of CS and CR P1798 [³H]TA complexes with trypsin gave rise to a discrete 19-Å (Stokes radius) fragment that did not bind to DNA-cellulose. In all instances, the Stokes radii were determined on heat-activated (1 hr; 20°) [³H]TA-receptor complexes.

Our results suggest that differences in glucocorticoid-receptor complex interaction with the nucleus between CS and CR P1798 lymphocytes may be determined by receptor properties. Furthermore, our findings are consistent with the idea that DNA and/or other anionic species may be an important part of nuclear acceptor sites in both strains of tumor. Our data also support the hypothesis that the portion of the CS P1798 complex that is digested by chymotrypsin, i.e., the 61 28 Å region, may play an important role in modulating glucocorticoid-receptor complex interaction with the nucleus in CS tumor lymphocytes.

¹ Supported by NIH Grants CA 14987 and P 30 14194.

² Scholar of the Leukemia Society of America, Inc. To whom requests for reprints should be addressed.

Received 6/12/80. Accepted 10/ 8/80.