S 100 A 8 ( S 100 calcium binding protein A 8 )

Note S100A8 belongs to the S100/calgranulin family of small non-ubiquitous cytoplasmic Ca -binding proteins of EF-hand type. The proteins were referre d to "S100" because of their solubility in saturated ammonium sulphate solution. Sixteen of 21 members are localised in a cluster on human chromosome 1q21 . The clustered organization of these S100 genes is conserved during evolution (Ridinger et al., 1998). A comparison between man and mouse has shown that during evolution, the colinearity of the S100 gene cluster has been destroyed by some inversions. However, the colocalization of the myeloid expresse d S100 genes such as S100A8, S100A9, and S100A12 is conserved. It has been speculated, that the structu ral integrity of that part of the locus is necessary fo r the coordinated expression of these genes (Nacken et al ., 2001). Remarkably, the S100 gene cluster is located in clo se proximity to a region which has been frequently rearranged in human cancer (Carlsson et al., 2005) and to the epidermal differentiation complex (EDC) (Mischke et al., 1996). EDC is a cluster of genes o n chromosome 1q21 encoding proteins that fulfil important functions in terminal differentiation in the human epidermis, including filaggrin, loricrin and others. In addition, linkage analyses have identifi ed a psoriasis susceptibility region, the PSORS4 locus, that is close to the S100 gene cluster (Hardas et al., 1 996; Semprini et al., 2002). These data are important indications for the involvement of S100 genes in inflammatory as well as neoplastic disorders. It ha s been speculated that the rearrangements result in a deregulated expression of S100 genes associated wit h neoplasia.