Coactivator cross-talk specifies transcriptional output
Coactivator cross-talk specifies transcriptional output
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DOI：
10.1101/gad.1418806
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发表时间：
2006-06-01
影响因子：
10.5
通讯作者：
Tjian, Robert
中科院分区：
文献类型：
--
作者：
Marr, Michael T., II;Isogai, Yoh;Tjian, Robert
细胞通常在转录水平上微调基因表达，以对给定的环境或发育刺激产生适当的反应。必须平衡对基因表达的正面和负面影响才能产生正确的 mRNA 合成水平。为此，细胞使用几类调节共激活因子复合物，包括两个核心参与者：TFIID 和介体 (MED)，以增强激活的转录。这两种复合物都整合激活剂信号并将其传送到基础装置。有趣的是，许多发起人都需要这两种监管复合体，尽管乍一看它们似乎是多余的。在这里，我们在果蝇细胞中使用 RNA 干扰 (RNAi) 来选择性地消耗 MED 和 TFIID 复合物的亚基，以剖析这些复合物中的每一个在调节激活转录中的贡献。我们通过分析异质细胞群和单细胞水平的直接因子招募，利用金属硫蛋白基因对重金属的强烈反应作为转录激活模型。有趣的是，我们发现 MED 和 TFIID 在功能上相互作用，调节对金属的转录反应。金属反应元件结合转录因子-1 (MTF-1) 招募 TFIID，然后 TFIID 结合启动子 DNA，建立一个用于启动转录的“检查点复合物”，随后在招募 MED 复合物时激活该复合物。只有当这两种共激活剂的活性达到平衡时，内源金属硫蛋白基因才能达到适当的表达水平。令人惊讶的是，我们发现相同的激活子（MTF-1）需要不同的共激活子亚基，具体取决于核心启动子的背景。最后，我们发现多亚基共激活复合物的稳定性可能因单个亚基的丢失而受到损害，这强调了转录激活组合控制的潜力。
Cells often fine-tune gene expression at the level of transcription to generate the appropriate response to a given environmental or developmental stimulus. Both positive and negative influences on gene expression must be balanced to produce the correct level of mRNA synthesis. To this end, the cell uses several classes of regulatory coactivator complexes including two central players, TFIID and Mediator (MED), in potentiating activated transcription. Both of these complexes integrate activator signals and convey them to the basal apparatus. Interestingly, many promoters require both regulatory complexes, although at first glance they may seem to be redundant. Here we have used RNA interference (RNAi) in Drosophila cells to selectively deplete subunits of the MED and TFIID complexes to dissect the contribution of each of these complexes in modulating activated transcription. We exploited the robust response of the metallothionein genes to heavy metal as a model for transcriptional activation by analyzing direct factor recruitment in both heterogeneous cell populations and at the single-cell level. Intriguingly, we find that MED and TFIID interact functionally to modulate transcriptional response to metal. The metal response element-binding transcription factor-1 (MTF-1) recruits TFIID, which then binds promoter DNA, setting up a "checkpoint complex" for the initiation of transcription that is subsequently activated upon recruitment of the MED complex. The appropriate expression level of the endogenous metallothionein genes is achieved only when the activities of these two coactivators are balanced. Surprisingly, we find that the same activator'(MTF-1) requires different coactivator subunits depending on the context of the core promoter. Finally, we find that the stability of multi-subunit coactivator complexes can be compromised by loss of a single subunit, underscoring the potential for combinatorial control of transcription activation.