TATA box‐independent transcription of the human tissue plasminogen activator gene initiates within a sequence conserved in related genes

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Abstract
Transcription of the human tissue-type plasminogen activator (tPA) gene has been reported to initiate from a single site proximal to a TATA box motif (1985, J. Biol. Chem. 260, 11223–11230). In this study, we utilized primer extension analysis to evaluate the tPA mRNA start site in phorbol-12-myristate 13-acetate (PMA) induced WI-38 man lung fibroblast cells. Whilst some tPA mRNA initiated from the predicted TATA-proximal location (+1), a 10-fold greater proportion of tPA mRNA transcripts initiated 110 bases downstream from a sequence conserved and utilized as the TATA-independent transcription start site in the rodent tPA genes. Moreover, the transfection and expression in different cell types of a cosmid containing the entire human tPA gene resulted in utilization of the same downstream (+110) start site. We propose that this, rather than the previously published position, is the major transcriptional initiation point for the human tPA gene. A core sequence (5′-CAGAGCTG-3′) was identified which is common to the TATA-independent mRNA start sites of the human, mouse and rat tPA genes, and which demonstrates only partial similarity to sequences found at the initiation point of other TATA-independent genes.