Platelet-derived growth factor-inducible gene JE is a member of a family of small inducible genes related to platelet factor 4

The platelet-derived growth factor-inducible gene JE was found to encode a 148-residue basic (pI = 10.4) secretory protein which shows striking similarity to the gene products of a family of small inducible genes (SIG), LD78, TCA3, IP10, 3-10C, 9E3/pCEF4, and gro/MGSA, and to several of the proteins secreted from platelet alpha-granules. Members of the SIG family have spatially conserved cysteine residues that vary in distance by only one amino acid residue as well as conserved proline residues at analogous sites. Hydrophilicity plots show alternating hydrophobic and hydrophilic domains which are similar for all members of the SIG family except IP10 and platelet factor 4, which show similarities to each other. The genomic organization of SIG family members is similar in the location of the splice junctions and the number of introns and exons, suggesting that they were derived from a common ancestor. The collective evidence suggests that a family of inducible cytokines, which are mitogenic or chemotactic, may act as intercellular coordinators of diverse responses designed to combat infection and promote the healing and regeneration of injured tissue.