STRUCTURAL-PROPERTIES OF 3.0-KB AND 3.2-KB TRANSCRIPTS ENCODING PLATELET-DERIVED ENDOTHELIAL-CELL GROWTH-FACTOR THYMIDINE PHOSPHORYLASE IN A431-CELLS

Platelet-derived endothelial cell growth factor/thymidine phosphorylas e (PD-ECGF/TP) is a 90 kDa protein consisting of two non-covalently as sociated subunits. In addition to the previously identified 1.8 kiloba se (kb) PD-ECGF/TP mRNA, the human epidermoid carcinoma cell line A431 was found to express 3.0 kb and 3.2 kb transcripts. cDNA cloning of t he larger transcripts revealed that they contain long 5' leader sequen ces of 1.5 kb and 1.7 kb, respectively, and the same open reading fram e encoding PD-ECGF/TP as that of the 1.8 kb transcript. Comparison wit h the published PD-ECGF/TP genomic sequence shows that the long 5' lea der sequence contain 7 of 8 copies of Sp-1 binding sites present in th e transcription promoter region of the 1.8 kb transcript.