Role of the Acetyltransferase p300 in Cellular Responses

描述（由申请人提供）：影响微管动力学的药物是最重要的一类化疗药物。具有临床意义的抗微管药物包括紫杉醇（紫杉醇）、长春花生物碱（长春花素和长春花素）、诺可唑和秋水仙碱。这些药物触发一个检查点，纺锤体检查点，它监视染色体与纺锤体的附着，并引起有丝分裂的停滞，通常随后是细胞凋亡。最近已经确定了几个参与这个检查点的细胞因子，然而，纺锤体组装错误或染色体附着在纺锤体上参与细胞周期机制的确切分子机制仍有待阐明。我们发现一种具有乙酰转移酶活性的转录辅激活因子p300可以增强紫杉醇引起的有丝分裂阻滞。

DESCRIPTION (provided by applicant): Drugs that affects the microtubule dynamics constitute one of the most important classes of chemotherapeutic agents. Anti-microtubule drugs of clinical relevance include paclitaxel (taxol), vinca alkaloids (vinblastin and vincrisitn), nocodazole and colchicine. These agents trigger a checkpoint, the spindle checkpoint, which monitors he attachment of chromosomes to the spindle, and elicits arrest in mitosis generally followed by apoptosis. Several cellular factors which participate in this checkpoint have recently been identified, however, the exact molecular mechanisms through which errors in spindle assembly, or chromosomes attachment to the spindle engage the cell cycle machinery remain to be elucidated. We made the novel finding that a transcription coactivator possessing acetyltransferase activity, p300, enhances the mitotic arrest elicited by taxol. Acetyltransferases belonging to the p300 family have been implicated in conveying adaptive responses in a variety of signal transduction pathways, through regulation of transcription of many cell-cycle regulatory genes. We now demonstrate that p300 associates with mitotic and interphase microtubules, it acetylates tubulin, and it favors tubulin polymerization in a taxol-dependent assay. Moreover p300 levels and its association with microtubules are significantly increased in taxol treated cells. Based on these results we hypothesize that p300 acts as an important effector of sensitivity of tumor cells to taxol, through its association with tubulin and through its activity as a transcription factor. To test this hypothesis we will: l)Identify the regions of p300 responsible for its interaction with microtubules and generate mutants with corrupted tubulin-binding ability (loss or gain of function, respectively). 2) Study how these mutants influence cytoskeleton architecture, spindle assembly and nuclear import of acetylated transcription factors in taxol treated cells. 3)Define the mechanisms by which p300 participates in cell cycle arrest and apoptosis induced by taxol and identify the molecular events occurring downstream of taxol which are influenced by p300. 4)Provide a rationale and a strategy for the design of molecules, such as peptides which mimics p300 effects on apoptosis, able to enhance chemosensitivity to taxol. Since mitotic spindle inhibitors constitute a growing class of anti-cancer agents, it is essential to understand molecular mechanisms of resistance and sensitivity. Thus, studies proposed in this application are expected to have important clinical implications.