Genomic structure and alternative splicing of 519, a gene expressed late after T cell activation

Relatively little is known about the transcriptional control of genes expressed late after T cell activation. We have identified four genes expressed 3 to 5 days after T cell activation by alloantigen or mitogen. Here we report the genomic organization of 519, one of these late T cell activation Ag. Analysis of the genomic clone revealed that 519 consists of six exons. Ribonuclease protection experiments indicated that the most abundant transcript arising from this region is an alternatively spliced form of 519, referred to as 520, which lacks exon 2 and is similar in sequence to NKG5, a cDNA identified in NK cells. These experiments also revealed the existence of two other alternatively spliced RNA transcripts, with heterogeneity in exon 2. Primer extension analysis and ribonuclease protection assays demonstrated that there are two prominent start sites for transcription; however, there is no evidence for the NKG5 transcript in T cells, indicating that NKG5 may represent a NK cell-specific form of 520. The 5′ flanking region of this gene contains several previously identified sequences involved in transcriptional regulation, as well as some potentially interesting novel conserved motifs.