Molecular cloning and structural characterization of the rat thymosin beta15 gene.

Thymosin beta15 is expressed in metastatic variants of Dunning rat prostatic carcinoma but not in a nonmetastatic variant. It is also upregulated in malignant human prostate cancers and was shown to be a predictive marker for patient outcome in prostate cancer. To explore the molecular mechanism of transcriptional regulation of thymosin beta15, we isolated and characterized the rat thymosin beta15 gene. The gene appears to exist as a single copy in the rat genome and to comprise three exons distributed over 2kb. The transcription start site was defined by primer extension analysis at 30 bp upstream of the translation start site. Sequence analysis of the 5′-flanking region of the transcription start site revealed properties consistent with promoter activity. The promoter region is GC rich and contains numerous consensus transcription factor binding sites as well as a GC box, but no TATA box. The transcriptional activity of the 5′-flanking region was analyzed by transient transfection of rat prostate cancer cells with firefly luciferase-encoding gene expression vector constructs. The isolated 5′ region showed significant promoter activity. The identification of the thymosin beta15 promoter could aid our understanding of the regulation of this gene and its enhanced expression in human cancer.

大鼠胸腺素β15基因的克隆和结构分析。

胸腺素β15在Dunning大鼠前列腺癌的转移变体中表达，但在非转移变体中不表达。它还在恶性人类前列腺癌中上调，并显示为前列腺癌患者预后的预测标志。为了探索胸腺素β15转录调控的分子机制，我们分离并鉴定了大鼠胸腺素β15基因。该基因似乎在大鼠基因组中以单拷贝存在，并包含分布在2kb以上的三个外显子。转录起始位点通过翻译起始位点上游30 bp的引物延伸分析来确定。转录起始位点5’-侧翼区的序列分析揭示了与启动子活性一致的性质。启动子区富含GC，包含许多共有转录因子结合位点和一个GC盒，但没有TATA盒。通过用编码萤火虫荧光素酶的基因表达载体构建体瞬时转染大鼠前列腺癌细胞来分析5’-侧翼区的转录活性。分离的5’区显示出显著的启动子活性。胸腺素β15启动子的鉴定有助于我们理解该基因的调节及其在人类癌症中的增强表达。