The ability to convert the 4 S glucocorticoid receptor to the 7–8 S form is dependent on both RNA and protein factors

The protein composition of the avian progesterone receptor was analyzed by immune isolation of receptor complexes and gel electrophoresis of the isolated proteins. Nonactivated cytosol receptor was isolated in association with the 90-kilodalton (kDa) heat shock protein, hsp9O, as has been described previously. A 70-kDa protein was also observed and was shown by Western immunoblotting to react with an antibody specific to the 70-kDa heat shock protein. Thus, two progesterone receptor-associated proteins are identical, or closely related, to heat shock proteins. When the two progesterone receptor species, A and B, were isolated separately in the absence of hormone, both were obtained in association with hsp9O and the 70-kDa protein. However, activated receptor isolated from oviduct nuclear extracts was associated with the 70-kDa protein, but not with hsp9O. A hormone-dependent dissociation of hsp9O from the cytosolic form of the receptor complex was observed within the first hour of in vivo progesterone treatment, which could explain the lack of hsp9O in nuclear receptor complexes. In a cell-free system, hsp9O binding to receptor was stabilized by molybdate but disrupted by high salt. These treatments, however, did not alter the binding of the 70-kDa protein to receptor. Association of the 70-kDa protein with the receptor could be disrupted by the addition of ATP at elevated temperatures (23°C). The receptor-associated 70-kDa protein is an ATP-binding protein, as demonstrated by its affinity labeling with azido[32P]ATP. These results indicate that the two receptor-associated proteins interact with the progesterone receptor by different mechanisms and that they are likely to affect the structure or function of the receptor in different ways.

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“…receptors that interact with additional, less well characterized proteins (12,37,60) or with RNA (3,17,61).…”

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confidence: 99%

Binding of heat shock proteins to the avian progesterone receptor.

Kost¹,

Smith²,

Sullivan³

et al. 1989

Mol. Cell. Biol.

191

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“…These workers suggest that this protein interacts with the receptor on the chymotrypsin-sensitive domain and plays a role in regulating receptor-DNA interactions. This is the location that we have postulated as the site of interaction of RNA (Tymoczko & Lee, 1985), as well as non-steroid-binding protein factors (Tymoczko et al, 1987), with the receptor. We have also suggested that these factors may play a role in regulating receptor function.…”

Section: Discussionmentioning

confidence: 81%

Identification of a protein from rat liver cytosol that enhances activation of the glucocorticoid receptor

Tymoczko

Ahern

Unger

et al. 1988

Biochemical Journal

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We have identified a factor from rat liver cytosol that enhances the DNA-cellulose-binding ability of the glucocorticoid receptor and lowers the sedimentation value from 9-10 S to 4-5 S. Cytosol is prepared in the presence of molybdate, and unactivated receptor is isolated by chromatography on DEAE-cellulose in the presence of molybdate. This receptor sediments at 9-10 S and has little affinity for DNA. If the molybdate is removed and the receptor is incubated at 25 degrees C with the low-salt wash of the DEAE-cellulose column, DNA binding is enhanced by 50-600% relative to controls incubated with buffer only. In addition, the factor present in the low-salt wash converts the 9-10 S receptor into a mixture of 5 S and 4 S forms. The factor must be present during the incubation in order to exert its maximal effect. Factor added after the incubation has only marginal effects on the DNA-binding ability of the receptor, indicating that the factor does not increase the DNA-binding ability of activated receptor. Moreover, the factor is significantly less effective on receptor that has been activated before incubation with the factor. These results suggest that the factor acts as an activation enhancer. Preliminary characterization indicates that the activation enhancer is a trypsin-sensitive protein of approx. 70,000 Da, whose activation-enhancing properties are inhibited by ATP. RNAase A, which has effects similar to those described above on the 7-8 S receptor, does not mimic the effects of the activation enhancer on the 9-10 S receptor.

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Purification of Nontransformed Avian Progesterone Receptor

Smith¹,

Toft²

1990

Receptor Purification

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The ability to convert the 4 S glucocorticoid receptor to the 7–8 S form is dependent on both RNA and protein factors

Cited by 9 publications

References 17 publications

Binding of heat shock proteins to the avian progesterone receptor.

Binding of heat shock proteins to the avian progesterone receptor.

Identification of a protein from rat liver cytosol that enhances activation of the glucocorticoid receptor

Purification of Nontransformed Avian Progesterone Receptor

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