INTERACTION OF THE 90-KDA HEAT-SHOCK PROTEIN WITH NATIVE AND INVITRO TRANSLATED ANDROGEN RECEPTOR AND RECEPTOR FRAGMENTS

Androgen receptor (AR) from rat ventral prostate and AR synthesized in vitro by translation in rabbit reticulocyte lysate of AR mRNA, transcribed from a pGEM-4Z DNA template were compared by gel permeation chromatography and by sucrose gradient ultracentrifugation. Under non-activating conditions the AR from rat prostate migrated as an 8-9 S complex of approx. 300 kDa. The addition of chicken antibodies against HSP90 shifted this complex to the void volume of the column or to the bottom of the ultracentrifugation gradient. Under activating conditions, on the other hand, the AR migrated as a 110 kDa, 5.2 S protein and was no longer displaced by HSP90 antibodies. Under all these conditions, the behaviour of in vitro synthesized AR was very similar to that of AR from rat prostate. By selective use of restriction enzymes on the template of transcription AR mutants could be prepared from which an increasing part was deleted at their carboxy terminal end. The interaction with HSP90 was conserved for AR1-758 missing the last 145 amino acids, but was lost in AR1-703. Furthermore, a large internal deletion (ARd41-469) of the major part of the amino terminal half of the AR did not result in the loss of HSP90 binding. These results indicate that a specific subregion (amino acids 704-758) of the carboxy terminal half of the AR is required for the interaction with HSP90.