Acts as a transcriptional coregulator, that can have both coactivator and corepressor functions (PubMed:18025162, PubMed:23980096). Inhibits the DCSTAMP-repressive activity of TAL1, hence enhancing the access of the transcription factor MITF to the DC-STAMP promoter in osteoclast (PubMed:23980096). Plays a role in bone homeostasis; required as a positive regulator in TNFSF11//RANKL-mediated osteoclast fusion via a DCSTAMP-dependent pathway (PubMed:23980096). May also be required in the regulation of osteoblast differentiation (PubMed:23980096). Involved in the transcriptional corepression of NF-kappaB in macrophages. Plays a role as a regulator in the pro-inflammatory cascade (By similarity). 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 (PubMed:23980096). Expressed in the spleen and bone marrow, and to a lesser extent in the kidney, liver, brain, skin, heart and muscle (PubMed:23980096). Expressed predominantly in osteoclasts, and to a lesser extent in T-cells, B-cells and osteoblasts (PubMed:23980096). Expressed in macrophages (PubMed:18025162). Up-regulated by interleukin IL6 together with soluble interleukin receptor IL6R in astrocytes (PubMed:25903009). Up-regulated by interleukins such as IL1B or tumor necrosis factor TNF in astrocytes (at protein level) (PubMed:25903009). Up-regulated by interleukin IL6 together with soluble interleukin receptor IL6R in astrocytes (PubMed:25903009). Up-regulated also by other cytokines such as interleukin IL11, oncostatin M (OSM) and leukemia inhibitory factor (LIF) (PubMed:25903009). Up-regulated by interleukin such as IL1B or tumor necrosis factor TNF in astrocytes (PubMed:25903009). Up-regulated by lipopolysaccharide (LPS) (PubMed:25903009, PubMed:23980096). Up-regulated by interleukin IL10 in a STAT3-dependent manner in bone marrow derived macrophages (PubMed:18025162). Up-regulated by TNFSF11//RANKL in a c-Fos/FOS-dependent manner (PubMed:23980096). Mice display a severe osteopetrotic phenotype characterized with an increased bone mass (PubMed:23980096). Show a reduction in the osteoclast surface/bone surface and eroded surface/bone surface ratio, but the osteoclast number/bone surface ratio is normal (PubMed:23980096). Show also a reduction in nuclei/osteoclast ratio (PubMed:23980096). Exhibit an impairment in TNFSF11//RANKL-mediated osteoclast fusion (PubMed:23980096). Show a slight inhibition of osteoblast differentiation (PubMed:23980096). Belongs to the SBNO family.