pRb2/p130: from the mechanisms to gene therapy

描述（由申请人提供）：pRb2/pl30：从机制到治疗。视网膜母细胞瘤（RB）家族蛋白是在许多成人组织中正常表达的负细胞周期调节因子。每个RB蛋白结合并调节E2F转录因子的活性，刺激基因的转录需要通过S期进行。RBs-E2Fs抑制复合物与组蛋白去乙酰化酶（HDAC 1）相关，该酶可能通过从核小体突出的组蛋白尾部去乙酰化来抑制转录。由于启动子超甲基化和/或翻译后修饰（如乙酰化和磷酸化）导致基因沉默，每个RB家族蛋白的稳定性和功能活性都可能受到阻碍。虽然有一些迹象表明pRb/pl05功能活性的表观遗传或翻译后控制的作用，但关于RB家族其他成员的数据很少。然而，乙酰化和磷酸化可能不是完全独立的过程。磷酸化和乙酰化状态也可以通过决定泛素介导的降解的可能性来影响蛋白质的稳定性，泛素介导的降解被认为是程序性细胞死亡的早期事件，可能与细胞凋亡有关。因此，研究表明，pRb/p105的内部切割失败与诱导凋亡反应的抗性有关。到目前为止，还没有关于pRb2/pl30的类似数据报道。失控的细胞增殖和抑制的细胞凋亡共同构成了所有肿瘤进化发生的最小共同平台。这些研究的基本原理是确定表观遗传或翻译后修饰对pRb2/pl30的功能、稳定性、生化相互作用和降解的意义。我们将追求以下目标：/)Rb2/p130负调控细胞周期基因的转录，发挥其生长抑制功能。2) pRb2/p130基因沉默促进肿瘤进展的表观遗传事件。3) pRb2/pl30在诱导生长停滞和凋亡反应中的翻译后修饰。4) LSL-K-Ras G12D小鼠模型中pRb2/ pl30的生长抑制和凋亡功能与活化的KRas致癌信号之间的串扰。

DESCRIPTION (provided by applicant): pRb2/pl30: from the mechanisms to therapy. The retinoblastoma (RB) family proteins are negative cell-cycle regulators normally expressed in a number of adult tissues. Each RB protein binds to and modulates the activity of the E2F transcription factors that stimulate the transcription of genes needed to progress through the S phase. The RBs-E2Fs repressive complexes function in association with histone deacetylase (HDAC 1) which essentially repress transcription probably through deacetylation of histone tail that protrudes from nucleosome. The protein stability and the functional activity of each RB family protein can be hampered by gene silencing due to their promoter hypermethylation and/or by their post-translational modifications such as acetylation and phosphorylation. Although some indications are available about the role of epigenetic or post-translational control of pRb/pl05 functional activity, there are very few data about the other members of RB family. However, acetylation and phosphorylation may be not completely independent processes. Phosphorylation and acetylation status can influence also the protein stability by determining the probability of ubiquitin-mediated degradation, which it is though to be an early event in programmed cell death, possibly related to cell commitment to apoptosis. As a consequence, it has been shown that failure to the interior cleavage of pRb/p105 is associates with resistance to induction of apoptotic response. Up to now no similar data has been reported for pRb2/pl30. Deregulated cell proliferation together with suppressed apoptosis, constitute the minimal common platform upon which all neoplastic evolution occurs. The rationale for these studies is that the identification of significance of the epigenetic or post-translational modification on the function, stability, biochemical interactions and degradation of pRb2/pl30. We will pursue the following aims:/) Rb2/p130 negatively regulates the transcription of cell-cycle genes to exert its growth suppressive function. 2) Epigenetic events for pRb2/p130 gene silencing promoting tumor progression. 3) pRb2/pl30 post-translational modification during the induction of growth arrest and apoptotic response. 4) The cross talk between the pRb2/pl 30 growth suppressive and apoptotic function and the activated KRas oncogenic signals in the LSL-K-Ras G12D mouse model. These experiments will provide further insight into the post-translational modifications necessary to induce pRb2/p 130- dependent growth suppression and apoptosis. Finally, our results will be significant in that they will give us clues to the mechanisms underlying pRb2/p 130 activity and to characterize its role in tumorigenesis providing useful tools for design novel therapeutic strategies.