The opposing transcriptional activities of the two isoforms of the human progesterone receptor are due to differential cofactor binding
The opposing transcriptional activities of the two isoforms of the human progesterone receptor are due to differential cofactor binding
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DOI：
10.1128/mcb.20.9.3102-3115.2000
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发表时间：
2000-05-01
影响因子：
5.3
通讯作者：
McDonnell, DP
中科院分区：
文献类型：
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作者：
Giangrande, PH;Kimbrel, EA;McDonnell, DP
人孕酮受体（PR）以两种功能不同的亚型hPRA和hPRB存在。hPRB在大多数细胞和启动子竞争中起转录激活剂的作用，而hPRA是转录失活的，并且起类固醇激素受体转录活性的强配体依赖性反式显性阻遏物的作用。虽然hPRA介导的反式阻遏的确切机制还不完全清楚，但已经鉴定出人PR内的抑制结构域（ID），其对于hPRA的反式阻遏是必需的。有趣的是，虽然ID存在于两种hPR同种型中，但它仅在hPRA的情况下具有功能活性，这表明两种受体在细胞内采用不同的构象，这使得hPRA与一组不同于hPRB识别的辅因子相互作用。为了支持这一假设，我们使用噬菌体展示技术鉴定了，差异调节hPRA和hPRB转录活性的hPRA选择性肽。此外，使用体外和体内方法相结合，我们证明了陶受体表现出不同的辅因子相互作用。具体而言，它被确定为hPRA具有更高的亲和力的辅阻遏SMRT比hPRB，这种相互作用是由ID促进。有趣的是，抑制SMRT活性，无论是显性负突变体（C 'SMRT）或组蛋白脱乙酰酶抑制剂，逆转hPRA介导的transrepression但不转换hPRA的转录激活剂。总之，这些数据表明hPRA反式抑制类固醇激素受体转录活性的能力和其不能激活孕酮应答启动子的能力是通过不同的机制发生的。为此，我们观察到，hPRA，不像hPRB，是不能有效地招募激动剂结合后的转录辅激活因子GRIP 1和SRC-1。因此，尽管两种受体在其配体结合结构域内均含有已知为辅激活因子结合所需的序列，但PR以生产性方式与辅因子相互作用的能力受受体氨基末端内所含序列的调节。因此，我们建议，hPRA是转录失活，由于它不能有效地招募辅激活因子，此外，我们的实验表明，hPRA有效地与辅阻遏SMRT相互作用，这种活动允许它作为一个反式显性阻遏。
The human progesterone receptor (PR) exists as two functionally distinct isoforms, hPRA and hPRB. hPRB functions as a transcriptional activator in most cell and promoter contests, while hPRA is transcriptionally inactive and functions as a strong ligand dependent transdominant repressor of steroid hormone receptor transcriptional activity. Although the precise mechanism of hPRA-mediated transrepression is not fully understood, an inhibitory domain (ID) within human PR, which is necessary for transrepression by hPRA, has been identified. Interestingly, although ID is present within both hPR isoforms, it is functionally active only in the context of hPRA, suggesting that the two receptors adopt distinct conformations within the cell which allow hPRA to interact with a set of cofactors that are different from those recognized by hPRB, In support of this hypothesis, we identified, using phage display technology, hPRA-selective peptides which differentially modulate hPRA and hPRB transcriptional activity. Furthermore, using a combination of in vitro and in vivo methodologies, we demonstrate that the tao receptors exhibit different cofactor interactions. Specifically, it was determined that hPRA has a higher affinity for the corepressor SMRT than hPRB and that this interaction is facilitated by ID. Interestingly, inhibition of SMRT activity, by either a dominant negative mutant (C'SMRT) or histone deacetylase inhibitors, reverses hPRA-mediated transrepression hut does not convert hPRA to a transcriptional activator. Together, these data indicate that the ability of hPRA to transrepress steroid hormone receptor transcriptional activity and its inability to activate progesterone-responsive promoters occur by distinct mechanisms. To this effect, we observed that hPRA, unlike hPRB, was unable to efficiently recruit the transcriptional coactivators GRIP1 and SRC-1 upon agonist binding. Thus, although both receptors contain sequences within their Ligand-binding domains known to be required for coactivator binding, the ability of PR to interact with cofactors in a productive manner is regulated by sequences contained within the amino terminus of the receptors. We propose, therefore, that hPRA is transcriptionally inactive due to its inability to efficiently recruit coactivators, Furthermore, our experiments indicate that hPRA interacts efficiently with the corepressor SMRT and that this activity permits it to function as a transdominant repressor.