SSX1 can repress transcription, and this has been attributed to a putative Kruppel associated box (KRAB) repression domain at the N-terminus. However, from the analysis of these deletion constructs further repression activity was found at the C-terminus of SSX1. Which has been called the SSXRD (SSX Repression Domain). The potent repression exerted by full-length SSX1 appears to localise to this region [1].

1: A KRAB-related domain and a novel transcription repression domain in proteins encoded by SSX genes that are disrupted in human sarcomas. Lim FL, Soulez M, Koczan D, Thiesen HJ, Knight JC; Oncogene. 1998;17:2013-2018. PMID:9788446