The SAND domain (named after Sp100, AIRE-1, NucP41/75, DEAF-1) is a conserved ~80 residue region found in a number of nuclear proteins, many of which function in chromatin-dependent transcriptional control. These include proteins linked to various human diseases, such as the Sp100 (Speckled protein 100kDa) [ PUBMED:9636146 … expand

The SAND domain (named after Sp100, AIRE-1, NucP41/75, DEAF-1) is a conserved ~80 residue region found in a number of nuclear proteins, many of which function in chromatin-dependent transcriptional control. These include proteins linked to various human diseases, such as the Sp100 (Speckled protein 100kDa) [ PUBMED:9636146 ], NUDR (Nuclear DEAF-1 related), GMEB (Glucocorticoid Modulatory Element Binding) proteins [ PUBMED:10894151 ] and AIRE-1 (Autoimmune regulator 1) proteins.

Proteins containing the SAND domain have a modular structure; the SAND domain can be associated with a number of other modules, including the bromodomain, the PHD finger and the MYND finger. Because no SAND domain has been found in yeast, it is thought that the SAND domain could be restricted to animal phyla. Many SAND domain-containing proteins, including NUDR, DEAF-1 (Deformed epidermal autoregulatory factor-1) and GMEB, have been shown to bind DNA sequences specifically. The SAND domain has been proposed to mediate the DNA binding activity of these proteins [ PUBMED:9697411 PUBMED:11427895 ].

The resolution of the 3D structure of the SAND domain from Sp100b has revealed that it consists of a novel α/β fold. The SAND domain adopts a compact fold consisting of a strongly twisted, five-stranded antiparallel β-sheet with four α-helices packing against one side of the β-sheet. The opposite side of the β-sheet is solvent exposed. The β-sheet and α-helical parts of the structure form two distinct regions. Multiple hydrophobic residues pack between these regions to form a structural core. A conserved KDWK sequence motif is found within the α-helical, positively charged surface patch. The DNA binding surface has been mapped to the α-helical region encompassing the KDWK motif [ PUBMED:11427895 ].