Structure and Function of Novel Cytokine, SDF-1

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Stromal cell-derived factors 1alpha and 1beta are small cytokines belonging to the intercrine CXC subfamily and originally isolated from a murine bone-marrow stroma cell line by the signal seqluence trap method. cDNA and genomic clones of human SDF1alpha and SDF1beta (SDF1A and SDF1B) were isolated and characterized. cDNAs of SDF1alpha and SDF1beta encode proteins of 89 and 93 amino acids, respectively. SDF1alpha and SDF1beta sequences are more than 92% identical to those of the human conterparts. The genomic structure of the SDF1 gene revealed that human SDF1alpha and SDF1beta are encoded by a single gene and arise by altemative splicing. SDF1alpha and SDF1beta are encoded by 3 and 4 exons, respectively. Ubiquitous expression of the SDF1 gene, except in blood cells, was consistent with the presence of the GC-rich sequence in the 5' flanking region of the SDF1 gene, as is often the case in the "house keeping" genes. Although genes encoding other members of the intercrine family are localized on chromosome 4q or 17q, fluorescence in situ hybridization. Strong evolutionary conservation and unique chromosomal lacalization of the SDF1 gene suggest that SDF1alpha and SDF1beta may have important functions distinct from those of other members of the intercrine family.