AFF1 is a ubiquitous P-TEFb partner to enable Tat extraction of P-TEFb from 7SK snRNP and formation of SECs for HIV transactivation
AFF1 is a ubiquitous P-TEFb partner to enable Tat extraction of P-TEFb from 7SK snRNP and formation of SECs for HIV transactivation
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AFF1 是一种普遍存在的 P-TEFb 伙伴，能够从 7SK snRNP 中提取出 P-TEFb，并形成用于 HIV 反式激活的 SEC
DOI：
10.1073/pnas.1318503111
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发表时间：
2014-01-07
影响因子：
11.1
通讯作者：
Zhou, Qiang
中科院分区：
文献类型：
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作者：
Lu, Huasong;Li, Zichong;Zhou, Qiang
RNA聚合酶II的转录延伸产生全长RNA转录物，并在调节基因表达中起着普遍和突出的作用。正转录延伸因子B（positive transcription elongation factor，P-TEF B）是调控这一过程的重要转录因子之一。核心P-TEFb由细胞周期蛋白依赖性激酶9和细胞周期蛋白T（CycT）组成，存在于包括7SK小核核糖核蛋白颗粒（7SK snRNP）、超延伸复合物（SEC）和溴结构域蛋白4（Brd 4）-P-TEFb复合物的复合物网络中。本研究将AF 4/FMR 2家族成员1（AFF 1）鉴定为贯穿整个P-TEFb网络的核心P-TEFb的普遍存在的结合伴侣。通过增加HIV编码的反式激活（达特）蛋白对CycT 1的亲和力，AFF 1是达特从7SK snRNP提取P-TEFb和形成SEC以最大化HIV转录激活所必需的。正性转录延伸因子B（P-TEF B）通过诱导启动子近端暂停的聚合酶II转变为有效延伸状态来刺激RNA聚合酶延伸。P-TEFb本身通过与各种转录因子/辅因子可逆缔合以形成几种多亚基复合物来调节[例如，7SK小核核糖核蛋白颗粒（7SK snRNP）、超延伸复合物（SEC）和布罗莫结构域蛋白4（Brd 4）-P-TEFb复合物]，其构成控制细胞和HIV转录的P-TEFb网络。这些复合物被认为除了核心P-TEFb亚基细胞周期蛋白依赖性激酶9（CDK 9）和细胞周期蛋白T（CycT、T1、T2 a和T2 b）之外没有其他组分。在这里，我们表明，AF 4/FMR 2家族成员1（AFF 1）结合到CDK 9-CycT，并存在于所有主要的P-TEFb复合物和三重CDK 9-CycT-AFF 1复合物作为一个单一的单位内的P-TEFb网络转移。通过增加HIV编码的反式激活（达特）蛋白对CycT 1的亲和力，AFF 1促进达特从7SK snRNP提取P-TEFb和形成用于HIV转录的Tat-SEC。我们的数据确定AFF 1作为一个普遍存在的P-TEFb的合作伙伴，并证明，充分的达特反式激活需要完整的SEC。
Significance Transcriptional elongation by RNA polymerase II produces full-length RNA transcripts and plays a general and prominent role in regulating gene expression. The positive transcription elongation factor b (P-TEFb) is one of the most important transcription factors controlling this process. The core P-TEFb, consisting of cyclin-dependent kinase 9 and cyclin T (CycT), exists in a network of complexes that include the 7SK small nuclear ribonucleoprotein particle (7SK snRNP), the super elongation complexes (SECs), and the bromodomain protein 4 (Brd4)–P-TEFb complex. This study identifies AF4/FMR2 family member 1 (AFF1) as a ubiquitous binding partner of core P-TEFb throughout the entire P-TEFb network. By increasing the affinity of the HIV-encoded transactivating (Tat) protein for CycT1, AFF1 is required for Tat’s extraction of P-TEFb from 7SK snRNP and the formation of SECs for maximal HIV transcriptional activation. The positive transcription elongation factor b (P-TEFb) stimulates RNA polymerase elongation by inducing the transition of promoter proximally paused polymerase II into a productively elongating state. P-TEFb itself is regulated by reversible association with various transcription factors/cofactors to form several multisubunit complexes [e.g., the 7SK small nuclear ribonucleoprotein particle (7SK snRNP), the super elongation complexes (SECs), and the bromodomain protein 4 (Brd4)–P-TEFb complex] that constitute a P-TEFb network controlling cellular and HIV transcription. These complexes have been thought to share no components other than the core P-TEFb subunits cyclin-dependent kinase 9 (CDK9) and cyclin T (CycT, T1, T2a, and T2b). Here we show that the AF4/FMR2 family member 1 (AFF1) is bound to CDK9–CycT and is present in all major P-TEFb complexes and that the tripartite CDK9–CycT–AFF1 complex is transferred as a single unit within the P-TEFb network. By increasing the affinity of the HIV-encoded transactivating (Tat) protein for CycT1, AFF1 facilitates Tat’s extraction of P-TEFb from 7SK snRNP and the formation of Tat–SECs for HIV transcription. Our data identify AFF1 as a ubiquitous P-TEFb partner and demonstrate that full Tat transactivation requires the complete SEC.