ANALYSIS OF THE PROMOTER AND TRANSCRIPTION START SITES OF THE HUMAN THROMBOSPONDIN-2 GENE (THBS2)

To identify features of the human thrombospondin 2 gene (THBS2) import ant for regulation of expression, the sequences of 5 kb of the promote r/5' flank and 3 kb of transcribed and intronic DNA were determined. T wo repetitive sequences were found: an MLTlc element located 2.2 kb 5' of exon 1 and, further 5', 1.8 kb of a Tigger1 element. Putative tran scription factor binding sites that might be significant for TNBS2 reg ulation included p53, NF-kB, Sp1, Myc-CF1, NF-Y, CF1, AP1, and GATA si tes. Alignment of the promoter/5' flank sequence with the mouse Thbs2 promoter revealed 78% identity for a 450 bp region immediately upstrea m from the mouse transcription start site. No significant homology was detected between the human thrombospondin 2 and thrombospondin 1 prom oters. Comparison of the THBS2 genomic and cDNA sequences revealed tha t, in contrast to Thbs2, exon 1 is divided into exons 1A and 1B by a s mall (93 bp) intron. The transcription start site was investigated by a PCR procedure and by 5' RACE, and yielded a size for exon 1A of at l east 186 bp. Tissue-specific differences in transcription start sites were found, with transcript lengths in the order: fetal lung > adult l ung > fetal brain. These results suggest that tissue-specific differen ces in expression of the THBS2 gene may be determined, in part, by sel ection of the transcription start site and resulting differences in th e 5' untranslated region. (C) 1997 Elsevier Science B.V.