ANTAGONIST-OCCUPIED HUMAN PROGESTERONE B-RECEPTORS ACTIVATE TRANSCRIPTION WITHOUT BINDING TO PROGESTERONE RESPONSE ELEMENTS AND ARE DOMINANTLY INHIBITED BY A-RECEPTORS
ANTAGONIST-OCCUPIED HUMAN PROGESTERONE B-RECEPTORS ACTIVATE TRANSCRIPTION WITHOUT BINDING TO PROGESTERONE RESPONSE ELEMENTS AND ARE DOMINANTLY INHIBITED BY A-RECEPTORS
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DOI：
10.1210/me.7.10.1256
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发表时间：
1993-10-01
影响因子：
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通讯作者：
HORWITZ, KB
中科院分区：
文献类型：
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作者：
TUNG, L;MOHAMED, MK;HORWITZ, KB
当拮抗剂占据的类固醇受体具有激动剂样作用时，临床后果是严重的。我们提出的证据表明，当被孕酮拮抗剂占据时，人孕酮B受体(HPR(B))通过一种不需要规范的孕酮反应元件(PRE)的不寻常机制不适当地激活转录。在共转染前tk-氯霉素乙酰转移酶报告基因和hPR(B)表达载体的HeLa细胞中，不仅当受体被激动剂R5020激活时，而且在三种抗孕激素RU486、ZK112993和ZK98299的存在下，都能观察到强转录。被ZK98299占据的人PR(B)不与Pre结合，提示转录刺激不依赖于DNA结合。事实上，缺乏Pre的tk-氯霉素乙酰转移酶启动子-报告失去了激动剂的转录激活，但保留了三种拮抗剂的反式激活。非独立前拮抗剂诱导的转录需要hPR(B)具有完整的DNA结合域，但不需要hPR靶基因的特异性，因为结合雌激素反应元件的hPR(B)突变体仍然激活转录。似乎拮抗剂占据的HPR激活转录而不与Pre结合，可能是通过与拴系蛋白相互作用来实现的。即使是一个不是正常孕激素靶点的基因也可能被异常激活。人类细胞含有等摩尔量的hPR(B)和N端截短的自然同型hPR(A)。与hPR(B)不同，hPR(A)不被黄体酮拮抗剂转录激活。因此，我们测试了当两种受体亚型共表达时拮抗剂的作用，发现A-受体可以取消B-受体的不适当转录。因此，当两种受体形式都存在时，hPR(A)表型占主导地位。此外，由FOS/Jun亮氨酸拉链结构域-HPR嵌合体产生的纯HPR(B)/HPR(A)异二聚体也具有HPR(A)的转录失活表型。我们的研究表明，这两种HPR亚型不仅在功能上有很大的不同，而且拮抗剂占据的B受体的一些激动剂样转录效应也通过新的机制进行。
When antagonist-occupied steroid receptors have agonist-like effects, the clinical consequences are grave. We present evidence that human progesterone B-receptors (hPR(B)) when occupied by progesterone antagonists, inappropriately activate transcription by an unusual mechanism that does not require the canonical progesterone response element (PRE). In HeLa cells cotransfected with a PRE-tk-chloramphenicol acetyltransferase reporter and a hPR(B) expression vector, strong transcription is seen not only when receptors are activated by the agonist R5020, but also in the presence of the three antiprogestins, RU486, ZK112993, and ZK98299. Human PR(B) occupied by ZK98299 do not bind to a PRE, suggesting that the transcriptional stimulation is independent of DNA binding. Indeed, a tk-chloramphenicol acetyltransferase promoter-reporter lacking the PRE loses transcriptional activation by the agonist, but retains transactivation by the three antagonists. The PRE-independent antagonist-induced transcription requires that hPR(B) have an intact DNA-binding domain, but hPR target gene specificity is not required, because a hPR(B) mutant that binds an estrogen response element still activates transcription. It appears that antagonist-occupied hPR activate transcription without binding to a PRE, perhaps by interacting with tethering proteins instead. Even a gene that is not a normal progesterone target could be aberrantly activated. Human cells contain equimolar amounts of hPR(B) and the N-terminally truncated natural isotype, hPR(A). Unlike hPR(B), hPR(A) are not transcriptionally activated by progesterone antagonists. We, therefore, tested the effects of antagonists when the two receptor isotypes are coexpressed and found that A-receptors can annul the inappropriate transcription by B-receptors. Thus, when both receptor forms are present, the hPR(A) phenotype is dominant. Moreover, pure hPR(B)/hPR(A) heterodimers, produced by fos/jun leucine zipper domain-hPR chimeras, also have the inactive transcriptional phenotype of hPR(A). Our studies suggest not only that the two hPR isotypes are functionally quite different, but also that some of the agonist-like transcriptional effects of antagonist-occupied B-receptors proceed through novel mechanisms.