Characterization of the mouse gene, human promoter and human cDNA of TSCOTreveals strong interspecies homology

The regulation of gene expression in thymic epithelial cells is critical fo r T cell development. The mouse thymic epithelial gene Tscot encodes a prot ein with weak homology to bacterial 12 transmembrane co-transporters. Using competitive reverse transcription-polymerase chain reaction (RT-PCR), we s how that low level Tscot expression is detectable in several other tissues. Tscot was mapped to chromosome 4 and was also detected in other mammalian species by Southern blotting. The human cDNA clone showed 77% amino acid id entity with the mouse sequence. The highest conservation was in the TM regi ons and in a small segment of the central cytoplasmic loop. Genomic clones spanning 17164 bases of the Tscot gene revealed four exons with nine of the TM domains encoded in the first exon. The major transcriptional start site in mouse was identified by a primer extension analysis and confirmed by RT -PCR. Comparison of 1.7 kb of the human and mouse promoters identified six conserved possible regulatory elements, one containing a potential binding site for an interferon oc inducible factor. Finally, as a functional test, 3 kb of the murine promoter was used to create a transgenic mouse that expr esses enhanced green fluorescent protein message strongly in the thymus, we akly in the kidney and undetectably in the spleen, liver and heart. (C) 200 0 Published by Elsevier Science B.V.