SS18 (D6I4Z) Rabbit mAb #21792

ATP-dependent chromatin remodeling complexes play an essential role in the regulation of nuclear processes such as transcription and DNA replication and repair (1,2). The SWI/SNF chromatin remodeling complex consists of more than 10 subunits and contains a single molecule of either BRM or BRG1 as the ATPase catalytic subunit. The activity of the ATPase subunit disrupts histone-DNA contacts and changes the accessibility of crucial regulatory elements to the chromatin. The additional core and accessory subunits play a scaffolding role to maintain stability and provide surfaces for interaction with various transcription factors and chromatin (2-5). The interactions between SWI/SNF subunits and transcription factors, such as nuclear receptors, p53, Rb, BRCA1, and MyoD, facilitate recruitment of the complex to target genes for regulation of gene activation, cell growth, cell cycle, and differentiation processes (1,6-9).
SS18 is a protein that has been shown to be a part of the SWI/SNF complex (10, 11). The SS18-SSX fusion proteins are a result of in-frame fusions that fuse the SS18 gene on chromosome 18 with X chromosome genes SSX1, SSX2, and to a lesser extent SSX4 (12). Human synovial sarcoma (SS) accounts for 8-10% of all soft tissue malignancies and 95% of these malignancies express the recurrent translocation of the SS18 gene on chromosome 18 (12). The N-terminal SNH domain (SYT N-terminal homology domain) of the SS18 protein interacts with SWI/SNF chromatin remodeling complexes via the N terminal region of BRM and BRG1 subunits (13). Studies of the SS18-SSX fusion in SS suggest that endogenous SS18 competes with the mutant SS18-SSX fusion for occupancy in the SWI/SNF complexes resulting in the displacement of SNF5 (BAF47) subunit. Displacement of the SNF5 subunit results in altered function of the SWI/SNF complex that leads to deregulated expression of genes such as Sox2 in SS (12).
In addition, cytosolic SS18 isoforms also associate with F-actin in cytoskeletal organization (14). SS18 null mice do not develop beyond E9.5 and have defects in vascularization, cell migration, neural tube closure, and fusion within the embryonic-maternal membranes (14).