The essential role of cyclin-dependent kinase CRK9 in trypanosome pre-mRNA processing

总结 动体寄生虫布氏锥虫、克氏锥虫和利什曼原虫属。影响数百万 人类非洲锥虫病（HAT），恰加斯病，以及各种形式的 利什曼病。由于治疗这些被忽视的热带疾病的药物有限，而且往往有毒， 为了管理，寄生虫对现有药物的耐药性正在上升，重要的是开发新的化疗药物， 治疗策略我们的研究集中在锥虫基因表达上，因为潜在的 这些机制与人类宿主中的机制有很大不同。例如，多顺反子转录 蛋白质编码基因和前mRNA通过剪接前导反式剪接的加工是寄生虫特异性的步骤， mRNA合成和成熟。我们在T.细胞周期蛋白依赖性激酶的活性 (CDK)CRK9是反式剪接所必需的。通过产生表达类似物敏感性CRK9的细胞系， 没有野生型酶，我们可以在培养的细胞中以特异性方式化学抑制该酶。令人惊讶的是， 我们观察到在应用抑制剂后立即出现剪接阻断，这表明CRK9进行了必要的转录调控。 RNA加工机制上的可逆磷酸化。我们的初步数据显示CRK9的其中一个 底物是SR蛋白和已知的剪接因子TSR1，阻断CRK9活性会影响组装 剪接体是进行剪接反应的大型动态RNA-蛋白质复合物。 因此，我们将确定CRK9如何帮助或控制剪接过程的机制。此外，委员会认为， CDK代表高度可药物化的酶类别，并且CRK9与一种或多种非药物化酶形成不寻常的三聚体酶复合物。 异常L型细胞周期蛋白和动质体特异性蛋白，这表明CRK9是一个有前途的目标， 化疗干预因此，我们建议对酶复合物进行表征，并确定 最小的复合物是有活性的，并且可以重组表达，作为未来高通量的先决条件 抑制剂筛选。最后，基于初步数据，我们将检验CRK9是靶点的假设。 化合物SCYX-7158，其目前在针对HAT的临床试验中。

Summary The kinetoplastid parasites Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp. affect millions of people worldwide, causing Human African Trypanosomiasis (HAT), Chagas’ disease, and various forms of Leishmaniasis, respectively. Since drugs for these neglected tropical diseases are limited, often toxic and difficult to administer, and parasite resistance to existing drugs is on the rise, it is important to develop new chemo- therapeutic strategies. Our research is focused on trypanosome gene expression because the underlying mechanisms deviate substantially from those in the human host. For example, polycistronic transcription of protein coding genes and processing of pre-mRNA by spliced leader trans splicing are parasite-specific steps in mRNA synthesis and maturation. We discovered in T. brucei that the activity of the cyclin-dependent kinase (CDK) CRK9 is required for trans splicing. By generating a cell line that expresses analog-sensitive CRK9 and no wild-type enzyme, we could chemically inhibit the enzyme in specific manner in cultured cells. Surprisingly, we observed an instant splicing block after applying the inhibitor, suggesting that CRK9 carries out essential reversible phosphorylation on the RNA processing machinery. Our preliminary data indicate that one of CRK9’s substrate is the SR protein and known splicing factor TSR1, and that blocking CRK9 activity affects the assembly of the spliceosome, the large and dynamic RNA-protein complex that carries out the splicing reaction. Consequently, we will determine the mechanism of how CRK9 aids or controls the splicing process. Furthermore, CDKs represent a highly druggable enzyme class, and CRK9 forms an unusual trimeric enzyme complex with a deviant L-type cyclin and a kinetoplastid-specific protein, suggesting that CRK9 is a promising target for chemotherapeutic intervention. Therefore, we propose to characterize the enzyme complex and determine a minimal complex that is active and can be expressed recombinantly as prerequisite for future high throughput inhibitor screens. Finally, based on preliminary data, we will test the hypothesis that CRK9 is the target of the compound SCYX-7158 which is currently in clinical trials against HAT.