Tang Dan, Chen Chunjing, Liao Ga, Liu Jiaming, Liao Banghua, Huang QingQing, Chen Qianqian, Zhao Jiahui, Jiang Hui, Duan Jinsong, Huang Jin, Wang Kunjie, Wang Jiawei, Zhou Cuiyan, Chu Wendan, Li Wenqi, Sun Bo, Li Zhonghan, Dai Lunzhi, Fu Xianghui, Cheng Wei, Xue Yuhua, Qi Shiqian
1Department of Urology, State Key Laboratory of Biotherapy, West China Hospital, College of Life Sciences, Sichuan University, and Collaborative Innovation Center for Biotherapy, Chengdu, Sichuan 610041 China.
2School of Pharmaceutical Sciences, Xiamen University, Xiamen, Fujian 361102 China.
Cell Discov. 2020 Feb 18;6:7. doi: 10.1038/s41421-020-0142-6. eCollection 2020.
Super elongation complex (SEC) is a positive regulator of RNA polymerase II, which is required for HIV-1 proviral transcription. AFF1/4 is the scaffold protein that recruits other components of SEC and forms dimer depending on its THD domain (TPRL with Handle Region Dimerization Domain). Here we report the crystal structure of the human AFF4-THD at the resolution of 2.4 Å. The α4, α5, and α6 of one AFF4-THD mediate the formation of a dimer and pack tightly against the equivalent part of the second molecule in the dimer of AFF-THD. Mutagenesis analysis revealed that single mutations of either Phe1014 or Tyr1096 of AFF4 to alanine impair the formation of the AFF4 dimer. In addition, transactivation assay also indicated that Phe1014 and Tyr1096 of AFF4 are critical to the transactivation activity of AFF4. Interestingly, the corresponding residues Phe1063 and Tyr1145 in AFF1 have an effect on the transactivation of HIV-1 provirus. However, such mutations of AFF1/4 have no effect on the interaction of AFF1/4 with other subunits of the SEC. Together, our data demonstrated that the dimerization of AFF1/4 is essential to transactivation of HIV-1 provirus.
超级延伸复合物（SEC）是RNA聚合酶II的正向调节因子，是HIV-1前病毒转录所必需的。AFF1/4是一种支架蛋白，可招募SEC的其他组分，并根据其THD结构域（带有柄区域二聚化结构域的TPRL）形成二聚体。在此，我们报道了分辨率为2.4Å的人AFF4-THD的晶体结构。一个AFF4-THD的α4、α5和α6介导二聚体的形成，并与AFF-THD二聚体中第二个分子的等效部分紧密堆积。诱变分析表明，AFF4的Phe1014或Tyr1096单突变为丙氨酸会损害AFF4二聚体的形成。此外，反式激活分析还表明，AFF4的Phe1014和Tyr1096对AFF4的反式激活活性至关重要。有趣的是，AFF1中相应的残基Phe1063和Tyr1145对HIV-1前病毒的反式激活有影响。然而，AFF1/4的此类突变对AFF1/4与SEC其他亚基的相互作用没有影响。总之，我们的数据表明，AFF1/4的二聚化对HIV-1前病毒的反式激活至关重要。
