To identify features of the human thrombospondin 2 gene (THBS2) important for regulation of expression, the sequences of 5 kb of the promoter/5' flank and 3 kb of transcribed and intronic DNA were determined. Two 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 transcription factor binding sites that might be significant for THBS2 regulation included p53, NF-kB, Sp1, Myc-CF1, NF-Y, CF1, AP1, and GATA sites. Alignment of the promoter/5' flank sequence with the mouse Thbs2 promoter revealed 78% identity for a 450 bp region immediately upstream from the mouse transcription start site. No significant homology was detected between the human thrombospondin 2 and thrombospondin 1 promoters. Comparison of the THBS2 genomic and cDNA sequences revealed that, in contrast to Thbs2, exon 1 is divided into exons 1A and 1B by a small (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 least 186 bp. Tissue-specific differences in transcription start sites were found, with transcript lengths in the order: fetal lung > adult lung > fetal brain. These results suggest that tissue-specific differences in expression of the THBS2 gene may be determined, in part, by selection of the transcription start site and resulting differences in the 5' untranslated region.
Bibliographical noteFunding Information:
This research was supported by a grant from the Minnesota Medical Foundation and by National Institutes of Health grant DE08229. We thank Sreelekha Devarayalu for assistance with the characterization of human THBS2 genomic clones, and Terry LaBell and Peter Byers for the gift of the THBS2 cDNA clone.
Copyright 2007 Elsevier B.V., All rights reserved.
- 5' Exon/intron
- 5' Flanking sequence
- Repetitive element
- Tissue-specific transcription initiation
- Transcription factor binding site