Acts as a transcriptional coregulator, that can have both coactivator and corepressor functions. Inhibits the DCSTAMP-repressive activity of TAL1, hence enhancing the access of the transcription factor MITF to the DC-STAMP promoter in osteoclast. Plays a role in bone homeostasis; required as a positive regulator in TNFSF11//RANKL-mediated osteoclast fusion via a DCSTAMP-dependent pathway. May also be required in the regulation of osteoblast differentiation (By similarity). Involved in the transcriptional corepression of NF-kappaB in macrophages (PubMed:18025162). Plays a role as a regulator in the pro-inflammatory cascade (PubMed:18025162). Interacts with TAL1; this interaction inhibits TAL1 occupancy of the DCSTAMP promoter, leading to the activation of the DCSTAMP promoter by the transcription factor MITF. Detected in macrophages. IL10 regulates expression in a STAT3-dependent way. Up-regulated by interleukin IL6 and soluble interleukin receptor IL6R in astrocytes (PubMed:25903009). Belongs to the SBNO family. Extended N-terminus.