Positive and negative TAFII functions that suggest a dynamic TFIID structure and elicit synergy with TRAPs in activator-induced transcription
Positive and negative TAFII functions that suggest a dynamic TFIID structure and elicit synergy with TRAPs in activator-induced transcription
复制标题
DOI：
10.1128/mcb.21.20.6882-6894.2001
复制
发表时间：
2001-10-01
影响因子：
5.3
通讯作者：
Roeder, RG
中科院分区：
文献类型：
--
作者：
Guermah, M;Tao, Y;Roeder, RG
人转录因子TFIID含有TATA结合蛋白（TBP）和几种TBP相关因子（TAF（II）（S））。为了阐明TFIID的结构组织和功能，我们表达并表征了编码人TAF（II）135（hTAF（II）135）的克隆cDNA的产物。比较远Western印迹显示hTAF（II）135与hTAF（II）20强烈相互作用，与hTAF（II）150适度相互作用，与hTAF（II）43和hTAF（II）250弱相互作用。与这些观察结果以及hTAF（II）20和hTAF（II）135分别与组蛋白H2 B和H2 A的序列关系一致，含有较高水平的hTAF（II）135的TFIID制剂也含有较高水平的hTAF（II）20，并且hTAF（II）20和hTAF（II）135之间的相互作用对于体外人TFIID组装是关键的。从功能的角度来看，已经发现hTAF（II）135与hTFIIA强烈和直接相互作用，并且（在还含有hTBP和hTAF（II）250的复合物内）与TFIIA特异性地协作以解除TAF（II）250介导的对核心启动子上的TBP结合和功能的抑制。最后，我们报告了TAF（II）和TRAP/介体复合物在激活转录中的功能协同作用，表现为hTAF（II）介导的基础转录抑制和随后的TRAP要求高绝对水平的激活转录和高的和更生理的激活/基础转录比。这些结果表明，一个动态的TFIID结构，其中从基础的hTAF（II）增强的抑制状态的启动子上的激活剂介导的激活状态的开关可以部分介导通过激活剂或辅激活剂与hTAF（II）135的相互作用。
Human transcription factor TFIID contains the TATA-binding protein (TBP) and several TBP-associated factors (TAF(II)(S)). To elucidate the structural organization and function of TFIID, we expressed and characterized the product of a cloned cDNA encoding human TAF(II)135 (hTAF(II)135). Comparative far Western blots have shown that hTAF(II)135 interacts strongly with hTAF(II)20, moderately with hTAF(II)150, and weakly with hTAF(II)43 and hTAF(II)250. Consistent with these observations and with sequence relationships of hTAF(II)20 and hTAF(II)135 to histones H2B and H2A, respectively, TFIID preparations that contain higher levels of hTAF(II)135 also contain higher levels of hTAF(II)20, and the interaction between hTAF(II)20 and hTAF(II)135 is critical for human TFIID assembly in vitro. From a functional standpoint, hTAF(II)135 has been found to interact strongly and directly with hTFIIA and (within a complex that also contains hTBP and hTAF(II)250) to specifically cooperate with TFIIA to relieve TAF(II)250-mediated repression of TBP binding and function on core promoters. Finally, we report a functional synergism between TAF(II)s and the TRAP/Mediator complex in activated transcription, manifested as hTAF(II)-mediated inhibition of basal transcription and a consequent TRAP requirement for both a high absolute level of activated transcription and a high and more physiological activated/basal transcription ratio. These results suggest a dynamic TFIID structure in which the switch from a basal hTAF(II)-enhanced repression state to an activator-mediated activated state on a promoter may be mediated in part through activator or coactivator interactions with hTAF(II)135.