Genetic analysis of DNA methylation in Neurospora crassa

异染色质和DNA甲基化的建立和维持对所有生物体的正常生长和发育至关重要。具体来说，异染色质和DNA甲基化对人类X染色体失活、染色体分离和寄生基因沉默至关重要。然而，控制异染色质形成和随后的DNA甲基化的机制目前尚不清楚。为了充分了解这些关键的人类发育过程，必须辨别异染色质和DNA甲基化形成的机制。基因组的异染色质区域通过几个共价修饰与它们活跃转录的正染色质区域区分开来。也就是说，异色DNA和相关的组蛋白被甲基化。虽然已经确定了几种催化DNA和组蛋白甲基化的蛋白质，但这些甲基转移酶蛋白质的调节现在才被认识到。对模式生物粗神经孢子菌（一种丝状真菌）的研究对于理解异染色质的形成至关重要。神经孢子虫与人类共享保守的DNA甲基化机制，但与许多高级真核生物不同，这种甲基化机制简单但必不可少。最近的研究发现了一种已知对核转运至关重要的蛋白质，它对组蛋白和DNA甲基化的建立都很重要，这表明这种蛋白质在调节甲基化机制中起着关键作用。这一建议将集中于描述核转运蛋白在DNA甲基化中的作用。使用细菌DNA腺嘌呤甲基化酶（dam）基因的翻译融合的DamID实验将分析该蛋白的基因组定位。该核转运蛋白对甲基化机制整体活性的影响将通过DNA甲基化机制标记组分的western blotting实验进行分析。该蛋白与绿色荧光蛋白（GFP）的翻译融合将分析该蛋白的细胞定位。共免疫沉淀实验将分析该核转运蛋白与H3K9me3机制相互作用的能力。此外，甲基化机制影响核转运蛋白基因组定位的能力将被研究。最后，将研究已知的核转运蛋白相互作用物在DNA甲基化中的作用。通过描述调控DNA甲基化机制所需的基因，我们将能够理解异染色质是如何在人类中正确建立的。此外，确定可能在癌症进展中发生突变的基因对于制定癌症患者的治疗或预防策略至关重要。

The establishment and maintenance of heterochromatin and DNA methylation is essential for the proper growth and development of all organisms. Specifically, heterochromatin and DNA methylation are essential for X- chromosome inactivation, chromosome segregation, and parasitic gene silencing in humans. However, the mechanisms controlling formation of heterochromatin, and subsequent DNA methylation, are presently unclear. In order to fully understand these critical human developmental processes, the mechanisms underlying the formation of heterochromatin and DNA methylation must be discerned. Heterochromatic regions of the genome are distinguished from their actively transcribed euchromatic counterparts by several covalent modifications. Namely, heterochromatic DNA and associated histone proteins are methylated. While several proteins have been identified that catalyze the methylation of DNA and histones, the regulation of these methyltransferase proteins is only now being appreciated. Studies in the model organism Neurospora crassa, a filamentous fungus, have been critical to understanding the formation of heterochromatin. Neurospora shares conserved DNA methylation machinery with humans, but unlike many higher eukaryotes, this methylation machinery is simple yet dispensable. Recent work has identified a protein that is known to be critical for nuclear transport as being important to establish both histone and DNA methylation, indicating that this protein has a critical role in regulating the methylation machinery. This proposal will focus on characterizing the role of the nuclear transport protein in DNA methylation. DamID experiments using translational fusions to the bacterial DNA Adenine Methylase (dam) gene will analyze the genomic localization of this protein. The influence of this nuclear transport protein on the global activity of the methylation machinery will be analyzed by western blotting experiments with tagged components of the DNA methylation machinery. Translational fusions of this protein to Green Fluorescent Protein (GFP) will analyze the cellular localization of this protein. Co-immunoprecipitation experiments will analyze the ability of this nuclear transport protein to interact with the H3K9me3 machinery. Moreover, the ability of the methylation machinery to influence the genomic localization of the nuclear transport protein will be investigated. Lastly, known interactors of the nuclear transport protein will be examined for their role in DNA methylation. By characterizing the genes required for the regulation of the DNA methylation machinery, we will be able to understand how heterochromatin is properly established in humans. In addition, identifying putative genes that could become mutated for the progression of cancer is essential to develop treatments or prevention strategies for cancer patients.