Regulation of Chromatin Remodeling and Transcription Involved in Tumor suppression and its Dysregulation in Oral Cancer

以前，我们已经报道了DRIL1，一个干旱(富含AX相互作用结构域)的DNA结合蛋白，受P53肿瘤抑制因子的调控。在这项研究中，我们研究了DRIL1在P53调控通路中的功能作用，以及其通路在口腔癌中的失调。在这里，我们发现DRIL1特异性地与p21Waf1/Cip1的启动子结合，p21Waf1/Cip1是一个对细胞周期停滞非常重要的靶基因，DRIL1结合位点的突变会减少p21启动子在p53过表达和DNA损伤后的反式激活。一直以来，DRIL1过表达诱导p21转录，DRIL1与p53共表达协同激活p21启动子。此外，我们还在促凋亡的P53靶基因中确定了DRIL1的活体结合部位。DRIL1和P53共表达协同诱导促凋亡基因表达，促进P53介导的细胞凋亡。钻头shRNA抑制P53-靶基因转录和…细胞凋亡提示DRIL1在P53靶基因表达和细胞凋亡中起重要作用。此外，DRIL1直接与P53和PML结合，PML是PML核体(NBS)的一个组成部分，参与P53翻译后修饰的许多蛋白质都是共定位的。我们发现，通过siRNA沉默DRIL1的表达肯定会损害P53的乙酰化和磷酸化，提示DRIL1在P53蛋白的翻译后修饰中起作用。在另一项研究中，我们发现Ser46上P53的磷酸化缺陷是HSC-3口腔癌细胞获得P53耐药性的原因。此外，共感染表达DRIL1和P53的腺病毒有效地诱导了P53耐药的HSC-3细胞的凋亡，同时诱导了促凋亡的P53靶基因。综上所述，这些结果表明，DRIL1是一种受P53调控的转录因子，它与P53协同作用，通过与P53靶基因的直接结合来加强P53依赖的转录并触发细胞凋亡，提示P53途径具有正向自我调节机制。较少

Previously, we have reported that DRIL1, an ARID (AX-rich interaction domain) DNA-binding protein, is regulated by p53 tumor suppressor. In this study, we investigated functional roles of DRIL1 in the p53 regulatory pathway, and dysregulation of its pathway in oral cancer. Here we show that DRIL1 specifically binds to the promoter of p21Waf1/Cip1, a p53-target gene important for cell cycle arrest Mutation of the DRIL1 binding sites diminished transactivation of the p21 promoter following p53 overexpression and DNA damage. Consistently, DRIL1 overexpression induces p21 transcription and co-expression of DRIL1 with p53 synergistically activates the p21 promoter. Furthermore, We also identified in vivo binding sites of DRIL1 in pro-apoptotic p53-target genes. Co-expression of DRIL1 and p53 synergistically induces pro-apoptotic gene expression and facilitated p53-mediated apoptosis. Silencing DRIL1 expression by DRILL shRNA down-regulated transcription of p53-target genes and apoptosis ind … More uced by DNA damage, indicating that DRIL1 play an important role in p53-target gene expression and apoptosis. Moreover, DRIL1 directly binds to p53 and PML, a component of PML nuclear bodies (NBs), in which many proteins involved in post translational modifications of p53 are co localized Consistently, we have found that silencing DRIL1 expression by siRNA surely impaired acetylation and phosphorylation of p53, suggesting that DRIL1 plays a role in the post-translational modifications of p53 protein. In a separate study, we found that the defect in phosphorylation of p53 on Ser46 accounts for the acquisition of the p53 resistance in HSC-3 oral cancer cells. Furthermore, coinfection of adenoviruses expressing DRIL1 and p53 efficiently induced apoptosis in p53-resistant HSC-3 cells accompanied by induction of pro-apoptotic p53-target genes. Collectively, these results demonstrate that DRIL1 is a p53-regulated transcription factor that cooperates with p53 to strengthen p53 dependent transcription and trigger apoptosis through its direct binding to p53-target genes, suggesting a positive autoregulatory mechanism of the p53 pathway. Less