Chou Wei-Yuan, Ho Ching-Liang, Tseng Mei-Ling, Liu Shu-Ting, Yen Li-Chen, Huang Shih-Ming
Department of Biochemistry, National Defense Medical Center, Taipei 114, Taiwan, ROC.
Int J Biochem Cell Biol. 2008;40(9):1826-34. doi: 10.1016/j.biocel.2008.01.014. Epub 2008 Jan 20.
Spot 14 is an acidic homodimeric protein with no sequence similarity to other mammalian gene products. Its biochemical function remains unclear. Recent studies have shown that the human Spot 14 locus is in the chromosomal region 11q13 and is frequently amplified in breast cancers, suggesting that it plays a role in the gene regulation involved in cell growth during tumorigenesis. Our previous work has demonstrated that human Spot 14 protein physically and functionally interacts with thyroid receptor in the regulation of malic enzyme gene expression. In this study, we investigated the subcellular distribution of human Spot 14 protein using enhanced green fluorescence protein and infer that its localization might be affected by thyroid hormone. Our results also demonstrate that the potential transactivation activity of human Spot 14 protein is regulated by its C-terminal region. Human Spot 14 protein is involved both in the regulation of malic enzyme promoter activity, and in the regulation of p53-dependent transactivation. It does not interact directly with p53, whereas it is able to directly interact with thyroid receptor and Zac1 (zinc finger protein which regulates apoptosis and cell cycle arrest 1) using glutathione-S-transferase pull-down assay. Hence, human Spot 14 protein might regulate the p53 target gene, p21(WAF1/Cip1), via its direct interaction with the thyroid receptor or other p53 coactivators, such as Zac1. These findings provide a molecular rationale for the role of human Spot 14 protein in the p53-dependent transcriptional activation of specific genes via diverse pathways in cells.
斑点14是一种酸性同二聚体蛋白，与其他哺乳动物基因产物没有序列相似性。其生化功能尚不清楚。最近的研究表明，人类斑点14基因座位于染色体区域11q13，在乳腺癌中经常扩增，这表明它在肿瘤发生过程中参与细胞生长的基因调控中发挥作用。我们之前的工作已经证明，人类斑点14蛋白在苹果酸酶基因表达的调控中与甲状腺受体发生物理和功能上的相互作用。在本研究中，我们使用增强型绿色荧光蛋白研究了人类斑点14蛋白的亚细胞分布，并推断其定位可能受甲状腺激素影响。我们的结果还表明，人类斑点14蛋白的潜在反式激活活性受其C末端区域调控。人类斑点14蛋白既参与苹果酸酶启动子活性的调控，也参与p53依赖性反式激活的调控。它不直接与p53相互作用，而通过谷胱甘肽-S-转移酶下拉试验能够直接与甲状腺受体和Zac1（调节细胞凋亡和细胞周期阻滞的锌指蛋白1）相互作用。因此，人类斑点14蛋白可能通过与甲状腺受体或其他p53共激活因子（如Zac1）的直接相互作用来调节p53靶基因p21（WAF1/Cip1）。这些发现为人类斑点14蛋白在细胞中通过多种途径参与特定基因的p53依赖性转录激活作用提供了分子理论依据。
