Genomic organization of the CC chemokine MIP-3 α/CCL20/LARC/EXODUS/SCYA20, showing gene structure, splice variants, and chromosome localization

Abstract

We describe the genomic organization of a recently identified CC chemokine, MIP3α/CCL20 (HGMW-approved symbol SCYA20). The MIP-3α/CCL20 gene was cloned and sequenced, revealing a four exon, three intron structure, and was localized by FISH analysis to 2q35–q36. Two distinct cDNAs were identified, encoding two forms of MIP-3α/CCL20, Ala MIP-3α/CCL20 and Ser MIP-3α/CCL20, that differ by one amino acid at the predicted signal peptide cleavage site. Examination of the sequence around the boundary of intron 1 and exon 2 showed that use of alternative splice acceptor sites could give rise to Ala MIP-3α/CCL20 or Ser MIP-3α/CCL20. Both forms of MIP-3α/CCL20 were chemically synthesized and tested for biological activity. Both flu antigen plus IL-2-activated CD4+ and CD8+ T lymphoblasts and cord blood-derived dendritic cells responded to Ser and Ala MIP-3α/CCL20. T lymphocytes exposed only to IL-2 responded inconsistently, while no response was detected in naive T lymphocytes, monocytes, or neutrophils. The biological activity of Ser MIP-3α/CCL20 and Ala MIP-3α/CCL20 and the tissue-specific preference of different splice acceptor sites are not yet known.