Differential requirements of Hsp90 and DNA for the formation of estrogen receptor homodimers and heterodimers.

The two estrogen receptor (ER) subforms, ERalpha and ERbeta, are capable of forming DNA-binding homodimers and heterodimers. Although binding to DNA is thought to stabilize ER dimers, how ERalpha/alpha, ERbeta/beta, and ERalpha/beta dimerization is regulated by DNA and the chaperone protein Hsp90 is poorly understood. Using our highly optimized bioluminescence resonance energy transfer assays in conjunction with assays for transcriptional activation of ERs, we determined that DNA binding appears to play a minor role in the stabilization of ER dimers, especially in the case of ERbeta/beta homodimers. These findings suggest that ER dimers form before they associate with chromatin and that DNA binding plays a minor role in stabilizing ER dimers. Additionally, although Hsp90 is essential for the proper dimerization of ERalpha/alpha and ERalpha/beta, it is not required for the proper dimerization of ERbeta/beta. Despite this, Hsp90 is critical for the estrogen-dependent transcriptional activity of the ERbeta/beta homodimer. Thus, Hsp90 is implicated as an important regulator of distinct aspects of ERalpha and ERbeta action.

热休克蛋白90和DNA对雌激素受体同源二聚体和异源二聚体形成的不同需求。

两种雌激素受体(ER)亚型ERα和ERβ能够形成DNA结合的同源二聚体和异源二聚体。虽然与DNA结合被认为可以稳定ER二聚体，但是ERα/α，ERβ/β和ERα/β二聚体是如何被DNA和伴侣蛋白Hsp90调节的却知之甚少。使用我们高度优化的生物发光共振能量转移试验结合ers转录激活试验，我们确定DNA结合似乎在ER二聚体的稳定中起次要作用，特别是在ERβ/β同源二聚体的情况下。这些发现表明ER二聚体在与染色质结合之前形成，DNA结合在稳定ER二聚体中起次要作用。此外，尽管Hsp90对于erα/α和erα/β的正确二聚化是必需的，但对于erβ/β的正确二聚化不是必需的。尽管如此，Hsp90对于ERbeta/beta同型二聚体的雌激素依赖性转录活性是至关重要的。因此，Hsp90被认为是ERalpha和ERbeta作用不同方面的重要调节因子。