The B-cell CLL/lymphoma 7 (BCL7) protein family members drive gene expression changes via interactions with the Brahma Related Gene 1 (BRG1) Helicase-Sant Associated domain (HSA) domain [24 hours]

The SWI/SNF complex remodels chromatin in an ATP-dependent manner through the ATPase subunits BRG1 and Brm Chromatin remodeling alters nucleosome structure to change gene expression. However, aberrant remodeling and gene expression can result in cancer. We identified a family of SWI/SNF complex members, the BCL7 proteins, as critical components to drive BRG1-dependent gene expression changes. The BCL7 proteins have been implicated in B-cell lymphoma, but the characterization of their functional role within the SWI/SNF complex has not been fully explored. This study implicates their critical function alongside BRG1 to cause large scale changes in gene expression. Mechanistically, the BCL7 proteins bind to the HSA domain of BRG1 and require this domain for stable protein expression and binding to chromatin. These results provide a link between the HSA domain and the formation of a stable functional SWI/SNF remodeling complex through the interaction with the BCL7 proteins. The data shown here highlights the importance of proper formation of the SWI/SNF complex to drive critical biological functions, as losses of members that were once considered minor accessory components can cause severe loss of complex function. Overall design: Adrenacorticoid carcinoma cells were generated to inducibly express respective constructs and harvested for RNA-seq.

SWI/SNF复合物（SWI/SNF complex）可通过其ATP酶亚基（ATPase subunits）BRG1与Brm，以ATP依赖的方式（ATP-dependent manner）介导染色质重塑（chromatin remodeling）。染色质重塑通过改变核小体（nucleosome）结构调控基因表达（gene expression），而异常的染色质重塑与基因表达失调可诱发癌症（cancer）。本研究鉴定出SWI/SNF复合物的BCL7蛋白（BCL7 proteins）家族，其是介导BRG1依赖型基因表达改变（BRG1-dependent gene expression changes）的关键组分。此前已有研究将BCL7蛋白与B细胞淋巴瘤（B-cell lymphoma）相关联，但其在SWI/SNF复合物内的功能角色尚未得到完全阐明。本研究证实，BCL7蛋白可与BRG1协同发挥关键功能，进而引发全基因组范围的基因表达改变。机制层面，BCL7蛋白可结合BRG1的HSA结构域（HSA domain），且该结构域是BCL7蛋白稳定表达（stable protein expression）以及其结合染色质（binding to chromatin）能力的必需条件。本研究结果揭示了HSA结构域通过与BCL7蛋白相互作用（interaction），进而组装形成稳定且具有功能的SWI/SNF重塑复合物（stable functional SWI/SNF remodeling complex）的关联机制。本数据凸显了SWI/SNF复合物正确组装（proper formation）对于维持关键生物学功能（critical biological functions）的重要性：曾被认为是次要辅助组分（minor accessory components）的亚基缺失，可导致复合物功能严重丧失（severe loss of complex function）。
实验整体设计（Overall design）：构建可诱导表达（inducibly express）相应构建体（respective constructs）的肾上腺皮质癌细胞（Adrenacorticoid carcinoma cells）系，收集细胞样本用于RNA测序（RNA-seq）。