Here's a third abstract by McDonnell:
OR48-3 HORMONE-DEPENDENT INTERACTIONS BETWEEN THE AMINO- AND CARBOXYL-TERMINAL REGIONS OF PROGESTERONE RECEPTOR DETECTED IN VITRO AND IN VIVO M J Tetel1, P H Giangrande2, D P McDonnell2, D P Edwards1, 1Pathology Dept., U. of Colorado HSC, Denver, CO, 2Dept of Pharmacology, Duke U. Medical Center, Durham, NC,
Human progesterone receptors (PR) exists as two isoforms, PR-B and the aminoterminally truncated PR-A. PR-A can function as a transcriptional repressor of PR-B and other steroid receptors in a cell and promoter specific manner. In the present study, we provide in vitro and in vivo evidence of interaction between the amino (N)- and carboxyl (C)-terminal regions of PR that may contribute to the functional differences of the two receptor isoforms. For in vitro studies, separately expressed N and C-terminal domains of PR were used in a pull down assay to detect and quantify interactions between nonfusion and polyhistidine-tagged proteins immobilized to a metal resin. In the presence of the progestin agonist R5020, the N-terminal domains of PR-B (BN, aa 1-535) and PR-A (AN, aa 165-535) physically interacted to a similar extent with the C-terminal ligand binding domain plus hinge sequences (hLBD, aa 634-933). N-C terminal interactions did not occur when the hLBD was unliganded or bound to the antagonist RU486, indicating these interactions are agonist-dependent. Addition of nuclear receptor co-activators (SRC-1 and CBP) increased hLBD association with N-terminal domains, suggesting these interactions are indirect. A mammalian two-hybrid assay was used to investigate N-C terminal interactions in vivo using the hLBD, BN and AN fused to either the GAL4 DBD or the VP16 transactivation domain. Consistent with the in vitro binding results, interactions between N and C terminal fusion proteins, as detected by reporter gene induction, occurred in a hormone-dependent fashion with antagonist decreasing these interactions. However, in contrast to the in vitro results, in Hela cells hLBD interacted with BN more efficiently than with AN, while in HepG2 cells hLBD associated more efficiently with AN than with BN. Interestingly, these cell-type specific differences correlate with the findings that PR-A in Hela cells is transcriptionally inactive and able to transrepress, while in HepG2 cells PR-A is transcriptionally active and unable to repress. In conclusion, these in vivo and in vitro data indicate that cell-type specific factor(s) mediate PR N-C domain interactions and may contribute to the functional differences between PR-A and PR-B.
Presentation Date, Time, Room: 27-Jun-98, 1:30P, CC-36
L=Special Session, N=Nurse Symposium, OR=Oral, P=Poster, S=Symposium |
