Study the Mechanism of Retinoblastoma Protein Mediated Androgen Receptor Transcriptional Repression Activity on DNA Replication

项目摘要 虽然AR被广泛地描述为转录激活因子，但最近有报道称，它 发挥转录抑制因子的作用，抑制基因的一个子集。重要的是，通过AR CHIP-SEQ和 我们在前列腺癌细胞中的转录组分析发现，直接受AR抑制的基因是高度 富含DNA复制功能，其中大多数基因在CRPC临床中持续增加 样本。我们随后发现，AR的这种直接转录抑制活性是由 雄激素刺激的低磷酸化Rb的募集。众所周知，雄激素还可以通过以下方式刺激生长 进一步激活AR转录激活驱动脂肪和固醇合成的基因，以及其他代谢功能， 与随后的细胞周期蛋白依赖性激酶激活和Rb过度磷酸化有关。血管紧张素转换酶过表达的研究 前列腺癌细胞可以克服这种生长刺激效应。这些发现表明，AR具有 Rb依赖的抗增殖功能，在Rb缺乏的CRPC细胞中可能受到损害 可通过阻断Rb的磷酸化而增强。这项建议的目标是确定 Rb的AR募集在调节DNA复制基因转录和细胞周期进程中的作用 前列腺癌肿瘤细胞(特异性靶点1)，确定AR与低磷酸化的相互作用的分子基础 Rb，并表征由AR招募到抑制位点的不同的Rb复合体(特定目标2)，以及 进行全基因组分析以确定Rb依赖的AR抑制位点并确定其机制 这些位点在前列腺癌细胞中的作用和功能作用(特定目标3)。

Project Summary While AR has been extensively characterized as a transcriptional activator, it was recently reported to function as a transcriptional repressor to suppress a subset of genes. Significantly, through AR ChIP-seq and transcriptome profiling in prostate cancer cells we have found that the directly AR-repressed genes are highly enriched for DNA replication function and majority of those genes were consistently increased in CRPC clinical samples. We then discovered that this direct transcriptional repression activity of AR was mediated by androgen-stimulated recruitment of hypophosphorylated Rb. Androgens is also known to stimulate growth by further AR transcriptional activation of genes driving lipid and sterol synthesis, and other metabolic functions, with subsequent cyclin dependent kinase activation and Rb hyperphosphorylation. Overexpression of AR in prostate cancer cells could overcome this growth stimulatory effect. These findings demonstrate that AR has an Rb-dependent anti-proliferative function, which may be compromised in CRPC cells with Rb-deficiency and could be enhanced by blocking Rb phosphorylation. The objective of this proposal is to determine the function roles of AR recruitment of Rb in regulating transcription of DNA replication genes and cell cycle progression of PCa tumor cells (specific aim 1), to determine the molecular basis for AR interaction with hypophosphorylated Rb and characterize the distinct Rb complex recruited by AR to the suppression sits (specific aim 2), and to conduct a genome wide analysis to identify Rb dependent AR suppression sites and determine the mechanism of actions and function roles of these sites in prostate cancer cells (specific aim 3).