A cluster of hematopoietic serine protease genes is found on the same chromosomal band as the human α/δ T-cell receptor locus

The chymotrypsin-like family of serine protease genes includes several members that are expressed exclusively in subsets of hematopoietic cells. For example, human neutrophil elastase and cathepsin G are expressed only in myelomonocytic precursors, and cytotoxic-T-cell serine proteases are found only in cytotoxic lymphocytes. We have used a cathepsin G cDNA probe to clone two cathepsin G-like genes (designated CGL-1 and CGL-2) from a human genomic library. We have determined that CGL-1 is identical to a previously identified gene (known as CCPI, CTLA I, or cytotoxic serine protease B) that is expressed only in activated cytotoxic T lymphocytes. We show here that cathepsin G, CGL-1, and CGL-2 are linked on an ≈50-kilobase locus found on human chromosome 14 at band q11.2. This gene cluster maps to the same chromosomal band as the α and δ T-cell receptor genes; this region is involved in most chromosomal translocations and inversions that are specifically associated with T-cell malignancies.