SMARCA4

SMARCA4 (also known as BRG1) encodes the ATPase catalytic subunit of the SWI/SNF chromatin-remodeling complex and uses ATP hydrolysis to alter nucleosome positioning, thereby regulating chromatin accessibility and transcriptional programs^[1][2]. Mechanistically, SMARCA4 functions as a core epigenetic regulator that coordinates gene expression, DNA damage-associated chromatin responses, and cell-state transitions through ATP-dependent chromatin remodeling^[1][3]. As one of two mutually exclusive SWI/SNF ATPase subunits, SMARCA4 is functionally distinct from SMARCA2 (BRM), with each complex containing either BRG1 or BRM as its catalytic engine rather than both simultaneously^[4][5]. This isoform distinction is biologically important because SMARCA4 deficiency can increase cellular dependence on SMARCA2-containing SWI/SNF complexes in specific tumor contexts^[4][6]. In disease settings, recurrent SMARCA4 inactivation has been identified across multiple malignancies and is strongly associated with chromatin dysregulation, including small cell carcinoma of the ovary, hypercalcemic type (SCCOHT), where loss of SMARCA4 protein is a defining molecular feature^[4][6][7]. Experimental studies further demonstrate that restoration of either SMARCA4 or SMARCA2 suppresses growth of SMARCA4-deficient SCCOHT cell lines, supporting a tumor-suppressive role for SWI/SNF ATPase activity in this model^[4]. For experimental applications, the SMARCA4 bromodomain recognizes acetylated histone H3K14 and has therefore emerged as a potential target for developing bromodomain-directed chemical probes and inhibitors that interrogate chromatin-remodeling mechanisms in cancer and epigenetic research^[3].