Cloning of ATAC, an activation‐induced, chemokine‐related molecule exclusively expressed in CD8+ T lymphocytes

Abstract

Abstract A cDNA clone, designated ATAC, was isolated from a collection of human T cell activation genes. Analysis of tissue distribution determined that ATAC mRNA of approxiamtely 0.9 kb is exclusively expressed in activated CD8 + T cells. Induction of the ATAC gene requires stimulation by both phorbol 12‐myristate 13‐acetate and Ca 2+ ionophore A23187 (“two‐signal gene”) and is fully abrogated by the immunosuppressive agent cyclosporin A. Upon stimulation, ATAC mRNA is detectable within 30 min, maximal expression is seen after 4 h. The polypeptide encoded by the open reading frame of ATAC mRNA is 114 amino acids long with a calculated M r of 12.52 kDa. The structural features predict the cleavage and secretion of a mature ATAC protein of approximately 10 kDa from the 12.52‐kDa precursor. ATAC is highly similar to a very recently identified murine molecule designated lymphotactin both at the cDNA (73.8% identity) and the protein (61.4% identity) levels, and related to members of the C‐C and C‐X‐C chemokine families. Two variants of the ATAC protein were expressed and tested for chemotaxis and Ca 2+ release on a variety of target cells. The ATAC gene was located to chromosome 1q23.