Characterization of CD13/APN endothelial cell transcripts.

(A) Schematic diagram showing the CD13/APN promoter regions used by epithelial cells (proximal promoter, generating a 3.4-kb transcript, top) and myeloid cells and fibroblasts (distal promoter, generating a 3.7-kb transcript, bottom). The translation start site (ATG) is identical in transcripts from each cell type and is followed in genomic DNA by the protein coding sequences (░). The proximal (1044-bp) and distal (1158-bp) promoter fragments are delineated by arrows. Additional untranslated sequences found only in transcripts originating from the distal promoter, ▨. Transcriptional start sites for each promoter are shown as diamonds. (B) CD13/APNexpression in various tissues as determined by Northern blot analysis of total cellular RNA. The identical blot is shown after it was stripped and reprobed with a 28S probe as a control for RNA integrity and loading. Lanes are identical in each panel, showing that theCD13/APN transcript in the KS1767 endothelial cell line comigrates with that of the HUVECs (3.4-kb) and is smaller than that found in myeloid cells (HL-60, KG1a, 3.7 kb). CD13/APNtranscripts are undetectable in EOMA cells.