Yang Shu-Ping, Lee Hui-Ju, Su Yeu
Department and Institute of Pharmacology, School of Medicine, National Yang-Ming University, Shih-Pai, Taipei, Taiwan, Republic of China.
Mol Cell Biochem. 2005 Apr;272(1-2):97-105. doi: 10.1007/s11010-005-7642-4.
Thymosin beta4 (Tbeta4), the actin-sequestering protein that regulates the polymerization and depolymerization of actins, is widely distributed in animal tissues. Expression of this gene in human cells is developmentally regulated and appears to play critical roles in tumorigenesis. As a first step toward analyzing the transcriptional regulation of human Tbeta4 (hTbeta4), we isolated the gene encoding this peptide and characterized its structure features. Human Tbeta4 gene comprises three exons and two introns distributed over 2 kb with its transcription start site at 72 bp upstream of the initiation codon. Expression of the chloramphenicol acetyltransferase (CAT) reporter constructs directed by various parts of the 5'-flanking region of this gene was evaluated by transient transfection assays using human colorectal carcinoma SW480 cells as hosts. Significant promoter activity was found in the -437 to +29 region of hTbeta4 gene even though it lacks both TATA and CCAAT boxes. However, cis-element(s) responsible for PMA-induced expression of Tbeta4 gene was not identified within its 1.5-kb 5'-flanking region. Taken together, our data provide crucial information for further dissection of the molecular mechanism(s) underlying aberrant expression of the Tbeta4 gene during malignant progression of human cancers.
胸腺素β4（Tbeta4）是一种肌动蛋白隔离蛋白，可调节肌动蛋白的聚合和解聚，广泛分布于动物组织中。该基因在人类细胞中的表达受发育调控，且似乎在肿瘤发生中起关键作用。作为分析人类Tbeta4（hTbeta4）转录调控的第一步，我们分离了编码该肽的基因并对其结构特征进行了表征。人类Tbeta4基因由三个外显子和两个内含子组成，分布在2 kb区域，其转录起始位点位于起始密码子上游72 bp处。使用人类结肠直肠癌SW480细胞作为宿主，通过瞬时转染试验评估了由该基因5'侧翼区域各部分指导的氯霉素乙酰转移酶（CAT）报告基因构建体的表达。尽管hTbeta4基因缺乏TATA盒和CCAAT盒，但在其-437至+29区域发现了显著的启动子活性。然而，在其1.5 kb的5'侧翼区域内未鉴定出负责佛波酯诱导的Tbeta4基因表达的顺式元件。综上所述，我们的数据为进一步剖析人类癌症恶性进展过程中Tbeta4基因异常表达的分子机制提供了关键信息。
