Protein SSX1 belongs to the family of highly homologous synovial sarcoma X (SSX) breakpoint proteins. SSX proteins are localized to the nucleus and expressed in testis and several types of cancers and, therefore, they are classified as C/T (cancer/testis) antigens. These proteins may function as transcriptional repressors. SSX1 genes have been involved in the t (X;18) translocation characteristically found in all synovial sarcomas. This translocation results in the fusion of the synovial sarcoma translocation gene on chromosome 18 to one of the SSX genes on chromosome X. The encoded hybrid proteins are probably responsible for transforming activity. Recombinant human SSX1 protein, fused to His-tag at N-terminus, was expressed in E.coli.