Institute of Biological Research and Biotechnology, National Hellenic Research Foundation, Athens, Greece.
FEBS J. 2010 Jul;277(14):3014-27. doi: 10.1111/j.1742-4658.2010.07710.x. Epub 2010 Jun 7.
The p73 gene possesses an extrinsic P1 promoter and an intrinsic P2 promoter, resulting in TAp73 and DeltaNup73 isoforms, respectively. The ultimate effect of p73 in oncogenesis is thought to depend on the apoptotic TA to antiapoptotic DeltaN isoforms' ratio. This study was aimed at identifying novel transcription factors that affect TA isoform synthesis. With the use of bioinformatics tools, in vitro binding assays, and chromatin immunoprecipitation analysis, a region extending -233 to -204 bp upstream of the transcription start site of the human p73 P1 promoter, containing conserved Sp1-binding sites, was characterized. Treatment of cells with Sp1 RNAi and Sp1 inhibitor functionally suppress TAp73 expression, indicating positive regulation of P1 by the Sp1 protein. Notably Sp1 inhibition or knockdown also reduces DeltaNup73 protein levels. Therefore, Sp1 directly regulates TAp73 transcription and affects DeltaNup73 levels in lung cancer. TAp73gamma was shown to be the only TA isoform overexpressed in several lung cancer cell lines and in 26 non-small cell lung cancers, consistent with Sp1 overexpression, thereby questioning the apoptotic role of this specific p73 isoform in lung cancer.
p73 基因拥有一个外在的 P1 启动子和一个内在的 P2 启动子，分别导致 TAp73 和 DeltaNup73 异构体的产生。p73 在致癌中的最终作用被认为取决于促凋亡的 TA 与抗凋亡的 DeltaN 异构体的比例。本研究旨在鉴定影响 TA 异构体合成的新转录因子。通过使用生物信息学工具、体外结合测定和染色质免疫沉淀分析，鉴定了人类 p73 P1 启动子转录起始位点上游 -233 到-204bp 的一个区域，该区域包含保守的 Sp1 结合位点。用 Sp1 RNAi 和 Sp1 抑制剂处理细胞可在功能上抑制 TAp73 的表达，表明 Sp1 蛋白对 P1 进行正向调控。值得注意的是，Sp1 抑制或敲低也会降低 DeltaNup73 蛋白水平。因此，Sp1 直接调控 TAp73 的转录，并影响肺癌中的 DeltaNup73 水平。在几种肺癌细胞系和 26 例非小细胞肺癌中，均显示出 TAp73gamma 是唯一过表达的 TA 异构体，与 Sp1 过表达一致，从而对该特定 p73 异构体在肺癌中的凋亡作用提出质疑。
