Mechanisms for glucocorticoid vs. progesterone receptor-specific gene regulation

比较GR-和PR调控基因转录的机制细节的任务随着我们发展了类固醇受体作用的理论模型而获得了额外的标准(Ong等人，2010年，《NACT学报》，U S A，1077107-7112)。这个模型的三个新特征及其相关的图形分析，允许关于类固醇受体调节的基因反式激活的前所未有的机制信息水平。首先，现在可以确定因子(竞争性抑制物、非竞争性抑制物、共激活剂等)所显示的动力学定义的作用类型。其次，通常可以定义因子相对于称为浓度限制步骤(CLS)的参照点的作用位置，该浓度限制步骤是酶动力学的速率限制步骤的稳态模拟。第三，该模型及其图形分析最近已扩展到同一分析中的两个相互竞争的因素的分析(Dougherty等人，2012，PLoS One，7，e30225)。与使情况更加模糊相反，这种竞争分析实际上产生了更多的机械性信息。这样的竞争分析不仅可以确定每个因素相对于CLS如何以及在哪里起作用，而且通常还可以揭示这两个因素相对于彼此的作用地点。因此，人们现在可以根据辅因子的生物功能组装出有序的反应序列，就像上位性分析一样，即使在辅因子的生化性质未知的情况下也是如此。一些辅因子的初步实验并没有揭示GR和PR作用之间的任何重大差异。我们最近与大卫·莱文斯博士(NCI，NIH)合作的研究发现了一种以细胞特有的方式对GR产生不同影响的辅因子。与所考察的其他因素一样，在这一新因素下，GR和PR之间没有显著差异。然而，杂交转录因子GAL/VP16也对GR做出类似的反应，因此我们似乎还没有发现区分不同转录因子的因子。尽管如此，这些研究对我们在分子水平上定义GRs和PR的作用以及了解它们在人类生理学中的作用的长期目标有很大贡献。

The task of comparing the mechanistic details of GR- vs. PR-regulated gene transcription gained additional criteria with our development of a theoretical model of steroid receptor action (Ong et al., 2010, Proc Natl Acad Sci U S A, 107, 7107-7112). Three novel features of this model, and its associated graphical analysis, permit an unprecedented level of mechanistic information regarding steroid receptor-regulated gene transactivation. First, it is now possible to determine the kinetically-defined type of action being displayed by the factor (competitive inhibitor, uncompetitive inhibitor, coactivator, etc.). Second, it is usually possible to define where the factor acts relative to a reference point called the concentration limiting step (CLS), which is the steady state analog of the rate limiting step of enzyme kinetics. Third, the model and its graphical analysis have recently been extended to the analysis of two competing factors in the same assay (Dougherty et al., 2012, PLoS ONE, 7, e30225). As opposed to making the situation more obscure, this competition assay actually yields greater mechanistic information. Not only can such competition assays determine how and where each factor acts, relative to the CLS, but the site of action of the two factors relative to each other is usually revealed. Thus, one can now assemble an ordered sequence of reactions based on the biological function of cofactors, much as in epistasis analysis, even when the biochemical properties of the cofactors are not known. Initial experiments with a several cofactors have not exposed any major differences between GR and PR action. Recent studies in our collaboration with Dr. David Levens (NCI, NIH) have uncovered one cofactor that differentially affects GR in a cell-specific manner. As with the other factors examined, no significant differences between GR and PR are seen with this new factor. However, the hybrid transcription factor GAL/VP16 also responds similarly to GR so we do not appear to have yet found a factor that discriminates between different transcription factors. Nonetheless, these studies greatly contribute to our long-term goal of defining the action of GRs vs. PRs at a molecular level and of understanding their role in human physiology.