College of Life Science, Northeast Forestry University, Harbin 150040, China.
College of Arts and Sciences, Winthrop University, Rock Hill, SC 29733, USA.
Nucleic Acids Res. 2022 May 20;50(9):4917-4937. doi: 10.1093/nar/gkac233.
As an oncogenic transcription factor, Yin Yang 1 (YY1) regulates enhancer and promoter connection. However, gaps still exist in understanding how YY1 coordinates coactivators and chromatin enhancer elements to assemble enhancers and super-enhancers. Here, we demonstrate that a histidine cluster in YY1's transactivation domain is essential for its formation of phase separation condensates, which can be extended to additional proteins. The histidine cluster is also required for YY1-promoted cell proliferation, migration, clonogenicity and tumor growth. YY1-rich nuclear puncta contain coactivators EP300, BRD4, MED1 and active RNA polymerase II, and colocalize with histone markers of gene activation, but not that of repression. Furthermore, YY1 binds to the consensus motifs in the FOXM1 promoter to activate its expression. Wild-type YY1, but not its phase separation defective mutant, connects multiple enhancer elements and the FOXM1 promoter to form an enhancer cluster. Consistently, fluorescent in situ hybridization (FISH) assays reveal the colocalization of YY1 puncta with both the FOXM1 gene locus and its nascent RNA transcript. Overall, this study demonstrates that YY1 activates target gene expression through forming liquid-liquid phase separation condensates to compartmentalize both coactivators and enhancer elements, and the histidine cluster of YY1 plays a determinant role in this regulatory mechanism.
作为一种致癌转录因子，Yin Yang 1（YY1）调节增强子和启动子的连接。然而，人们对于 YY1 如何协调共激活因子和染色质增强子元件来组装增强子和超级增强子的理解仍存在空白。在这里，我们证明 YY1 转录激活结构域中的组氨酸簇对于其形成相分离凝聚物是必不可少的，这种凝聚物可以扩展到其他蛋白质。该组氨酸簇对于 YY1 促进的细胞增殖、迁移、集落形成和肿瘤生长也是必需的。富含 YY1 的核斑点包含共激活因子 EP300、BRD4、MED1 和活性 RNA 聚合酶 II，与基因激活的组蛋白标记物共定位，但与抑制的组蛋白标记物不共定位。此外，YY1 结合 FOXM1 启动子中的共有基序以激活其表达。野生型 YY1，但不是其相分离缺陷突变体，连接多个增强子元件和 FOXM1 启动子形成增强子簇。一致地，荧光原位杂交（FISH）实验显示 YY1 斑点与 FOXM1 基因座及其新生 RNA 转录本共定位。总的来说，这项研究表明，YY1 通过形成液-液相分离凝聚物来激活靶基因表达，从而分隔共激活因子和增强子元件，而 YY1 的组氨酸簇在这种调节机制中起着决定性作用。
