CHARACTERIZATION OF THE 5' REGION OF THE MOUSE NATURAL KILLER RECOGNITION GENE

Abstract

The mouse Nktr (natural killer tumor recognition) gene was cloned and the 5' region characterized. The Nktr gene was found to be single copy and non-arranging and mapped to the distal end of mouse chromosome 9. This gene encodes for a 150 kilodalton protein homologous to cyclophilin, Nopp 140, and SR-containing proteins. Nktr expression is important for maintaining the lytic activity of natural killer cells. Eight exons and one alternate exon have been identified as well as a conserved intron sequence that may be important in the regulation of Nktr pre-mRNA splicing. Through the use of the Rnase protection assay, the Nktr transcriptional start site was identified and found to be 56 nucleotides upstream from the 5' end of a previously isolated cDNA sequence. The Nktr promoter region has features that are typical of a housekeeping gene, including a high G/C content, potential SP1 binding domains, and lack of TATA and CAAT boxes. Further upstream from the core promoter, there are several additional possible binding sites for CREB, AP-2, and Ets-1 binding proteins. To determine the activity of the Nktr promoter, beta-galactosidase reporter constructs driven by the Nktr promoter were generated. The activity of the constructs was equivalent in lymphocyte and fibroblast cell lines, suggesting that NK-TR protein expression is regulated by post-transcriptional mechanisms and not by the initiation of transcription.