Malecová Barbora, Caputo Valentina S, Lee Diane F, Hsieh James J, Oelgeschläger Thomas
a Marie Curie Research Institute; The Chart , Oxted , Surrey , United Kingdom.
Transcription. 2015;6(2):21-32. doi: 10.1080/21541264.2015.1052178.
TFIIA is an important positive regulator of TFIID, the primary promoter recognition factor of the basal RNA polymerase II transcription machinery. TFIIA antagonises negative TFIID regulators such as negative cofactor 2 (NC2), promotes specific binding of the TBP subunit of TFIID to TATA core promoter sequence elements and stimulates the interaction of TBP-associated factors (TAFs) in the TFIID complex with core promoter elements located downstream of TATA, such as the initiator element (INR). Metazoan TFIIA consists of 3 subunits, TFIIAα (35 kDa), β (19 kDa) and γ (12 kDa). TFIIAα and β subunits are encoded by a single gene and result from site-specific cleavage of a 55 kDa TFIIA(α/β) precursor protein by the protease Taspase1. Metazoan cells have been shown to contain variable amounts of TFIIA (55/12 kDa) and Taspase1-processed TFIIA (35/19/12 kDa) depending on cell type, suggesting distinct gene-specific roles of unprocessed and Taspase1-processed TFIIA. How precisely Taspase1 processing affects TFIIA functions is not understood. Here we report that Taspase1 processing alters TFIIA interactions with TFIID and the conformation of TFIID/TFIIA promoter complexes. We further show that Taspase1 processing induces increased sensitivity of TFIID/TFIIA complexes to the repressor NC2, which is counteracted by the presence of an INR core promoter element. Our results provide first evidence that Taspase1 processing affects TFIIA regulation of TFIID and suggest that Taspase1 processing of TFIIA is required to establish INR-selective core promoter activity in the presence of NC2.
TFIIA是TFIID的重要正向调节因子，TFIID是基础RNA聚合酶II转录机制的主要启动子识别因子。TFIIA拮抗TFIID的负向调节因子，如负辅因子2（NC2），促进TFIID的TBP亚基与TATA核心启动子序列元件的特异性结合，并刺激TFIID复合物中的TBP相关因子（TAFs）与TATA下游的核心启动子元件（如起始子元件（INR））相互作用。后生动物的TFIIA由3个亚基组成，即TFIIAα（35 kDa）、β（19 kDa）和γ（12 kDa）。TFIIAα和β亚基由单个基因编码，是蛋白酶Taspase1对55 kDa TFIIA(α/β)前体蛋白进行位点特异性切割的产物。已表明后生动物细胞根据细胞类型含有不同量的TFIIA（55/12 kDa）和经Taspase1加工的TFIIA（35/19/12 kDa），这表明未加工的和经Taspase1加工的TFIIA具有不同的基因特异性作用。Taspase1加工如何精确影响TFIIA的功能尚不清楚。在此我们报告，Taspase1加工改变了TFIIA与TFIID的相互作用以及TFIID/TFIIA启动子复合物的构象。我们进一步表明，Taspase1加工导致TFIID/TFIIA复合物对阻遏物NC2的敏感性增加，而INR核心启动子元件的存在可抵消这种增加。我们的结果首次证明Taspase1加工影响TFIIA对TFIID的调节，并表明在存在NC2的情况下，TFIIA的Taspase1加工是建立INR选择性核心启动子活性所必需的。
