Molecular cloning and structural characterization of the rat thymosin beta15 gene

Thymosin beta 15 is expressed in metastatic variants of Dunning rat prostat ic carcinoma but not in a nonmetastatic variant. It is also upregulated in malignant human prostate cancers and was shown to be a predictive marker fo r patient outcome in prostate cancer. To explore the molecular mechanism of transcriptional regulation of thymosin beta 15, we isolated and characteri zed the rat thymosin beta 15 gene. The gene appears to exist as a single co py in the rat genome and to comprise three exons distributed over 2 kb. The transcription start site was defined by primer extension analysis at 30 bp upstream of the translation start site. Sequence analysis of the 5'-flanki ng region of the transcription start site revealed properties consistent wi th promoter activity. The promoter region is GC rich and contains numerous consensus transcription factor binding sites as well as a GC box, but no TA TA box. The transcriptional activity of the 5'-flanking region was analyzed by transient transfection of rat prostate cancer cells with firefly lucife rase-encoding gene expression vector constructs. The isolated 5' region sho wed significant promoter activity. The identification of the thymosin beta 15 promoter could aid our understanding of the regulation of this gene and its enhanced expression in human cancer. (C) 2000 Elsevier Science B.V. All rights reserved.