Elucidating chromosome structure and function through the lens of SMC complexes and R-loops

对发芽酵母的研究提供了对所有细菌细胞生物学过程的基本见解 真核生物。它的研究也为理解和治疗人类疾病做出了重要贡献 比如糖尿病、先天残疾和癌症。我的实验室使用萌芽酵母来审问三个领域的 细胞生物学，染色体的高级结构，防止染色体损伤和 重新安排，以及减轻环境压力。 染色体的基本单位是染色质，它由DNA和相关蛋白质组成。 将染色质组织成更高级的结构对于高保真的染色体分离是必不可少的， DNA损伤的修复和基因表达的调节。组织的分子机制 染色质是细胞生物学中的主要谜团。在这个提案中，我们通过 SMC(染色体结构维护)蛋白家族成员粘附素的分析 复合体。粘附素通过将不同的染色质区域连接在一起来促进染色体的组织 染色体内的或染色体之间的。粘附素也会沿着染色体移位以挤出 循环。这一建议质疑了粘附素的拴系和环挤出的分子机制 这些活动的调节，以及它们对活细胞中染色体结构和功能的影响。 细胞还通过预防和修复染色体损伤来维持基因组的稳定性。染色体 损害通常是由执行固有的细胞过程中的错误造成的。事实上，在转录过程中，一个 RNA转录本可能错误地与同源双链DNA序列杂交 染色体产生一个RNA-DNA杂交体和一个移位的单链DNA。这种不同寻常的结构， 称为R环，可导致DNA损伤和染色体重排。在这里，我们提出了一些实验，以 理解为什么基因组中只有一部分R-环会导致DNA损伤，以及这种损伤是如何导致 大的染色体重排，这是癌细胞的共同特征。 最后，细胞压力也是由外部环境变化引起的。了解一些人如何 生物在极端环境变化中生存下来，在技术和概念上提供了关键的进步 生物学。我们研究酵母在干燥状态下存活的能力。我们证明了一种小蛋白的表达 酵母中的单糖是酵母在干燥状态下存活的必要条件和充分条件。这两个因素阻止了 体外模型蛋白的聚集和膜的调控。在这里，我们建议澄清 通过鉴定特定的细胞蛋白和细胞膜，这两种因子具有显著的生物学功能 它们在干燥过程中受到保护。这些研究将提供对蛋白质和 膜的动态平衡超越了干燥，并可能产生潜在的生物医学和 农业。

The study of budding yeast has provided fundamental insights into the cell biological processes of all eukaryotes. Its study has also made critical contributions to the understanding and treatment of human disorders like diabetes, congenital disabilities, and cancer. My laboratory uses budding yeast to interrogate three areas of cell biology, the higher-order structure of chromosomes, the prevention of chromosome damage and rearrangements, and the mitigation of environmental stress. The basic unit of chromosomes is chromatin, which is composed of the DNA and associated proteins. The organization of chromatin into higher-order structures is essential for high fidelity chromosome segregation, the repair of DNA damage, and the regulation of gene expression. The molecular mechanisms that organize chromatin are major mysteries in cell biology. In this proposal, we study chromatin organization through the analysis of cohesin, a member of the SMC (Structural Maintenance of Chromosomes) family of protein complexes. Cohesin contributes to chromosome organization by tethering together different chromatin regions within a chromosome or between chromosomes. Cohesin also translocates along a chromosome to extrude loops. This proposal interrogates the molecular mechanisms underlying cohesin's tethering and loop-extrusion activities, the regulation of these activities, and their impact on chromosome structure and function in living cells. Cells also maintain genome stability by preventing and repairing chromosome damage. Chromosome damage is often caused by errors in the execution of intrinsic cellular processes. Indeed, during transcription, an RNA transcript can erroneously hybridize with homologous double-stranded DNA sequences on the chromosomes to generates an RNA-DNA hybrid and a displaced single-stranded DNA. This unusual structure, called an R-loop, can cause DNA damage and chromosome rearrangements. Here, we present experiments to understand why only a subset of R-loops in a genome cause DNA damage and how this damage leads to the large chromosome rearrangements that are a common feature of cancer cells. Finally, cellular stress also arises from extrinsic environmental changes. Understanding how some organisms survive extreme environmental changes has provided critical technical and conceptual advances in biology. We study the ability of yeast to survive desiccation. We showed that the expression of a small protein and simple sugar in yeast is necessary and sufficient for yeast to survive desiccation. These two factors prevent the aggregation of model proteins and modulate membranes in vitro. Here, we propose to elucidate the remarkable biological functions of these two factors by identifying the specific cellular proteins and membranes that they protected during desiccation. These studies will provide fundamental insights into protein and membrane homeostasis beyond desiccation and may generate potential novel applications for biomedicine and agriculture.