Genetic and Molecular Dissection of Meiotic Silencing by Unpaired DNA

本项目的总体目标是阐明粗糙脉孢菌中一种新的基因沉默系统--不成对DNA减数分裂沉默（MSUD）的机制。 MSUD在生命周期的有性阶段的短暂二倍体期和随后的减数分裂期间起作用。 二倍体细胞检查整个基因组，并在同源配对阶段比较任何DNA片段与其同源物的配对。 任何与同源序列不配对的基因大小或更大的DNA片段都会产生序列特异性信号，随后使该未配对DNA以及与其同源的任何序列（无论它们是否配对）的表达沉默。 由于这一过程需要RNA指导的RNA聚合酶（可能是双链RNA），因此MSUD可能依赖于mRNA转录物的特异性破坏，这是RNA干扰（RNAi）和其他转录后基因沉默系统共享的机制。 由于它能够比较两个交配伙伴的基因组，MSUD代表了一种维护基因组完整性的防御系统，以及一种可能的物种形成隔离机制。 N. crassa是评估减数分裂沉默过程的极好模式生物，因为其上级遗传学和突变体选择、分子技术的简易性和全基因组序列信息的可用性。 遗传学、细胞生物学和其他方法将用于鉴定减数分裂沉默系统所需的机制和机制步骤。 对N. crassa将提供一个很好的模型，用于描述减数分裂期间靶向未配对DNA沉默的机制，这一过程可能对印记X染色体失活和许多其他现象很重要。 由于RNAi作为揭示基因功能的实验工具具有巨大的潜力，因此对MSUD和其他基于RNA的沉默系统的理解可能会对生物学所有领域的研究产生广泛的影响。 此外，P.I.参与了许多教学和辅导活动，并注册为罗纳德麦克奈尔学者计划，旨在促进贫困的第一代大学生和代表性不足的群体成员的研究生入学导师。

The overall goal of this project is to delineate the mechanism of Meiotic Silencing by Unpaired DNA (MSUD), a novel gene silencing system in Neurospora crassa. MSUD operates during the brief period of diploidy and the subsequent meiotic divisions in the sexual phase of the life cycle. The diploid cell examines the entire genome and compares the pairing of any DNA segment with its homologue during the homologous pairing stage. Any gene-sized or larger segments of DNA not paired with a homologous sequence generates a sequence-specific signal, which subsequently silences the expression of this unpaired DNA, as well as any sequences homologous to it, whether they are paired or not. Since an RNA-directed RNA polymerase (and presumably a double-stranded RNA species) is required for this process, MSUD is likely to depend on the specific destruction of mRNA transcripts, a mechanism shared by RNA interference (RNAi) and other post-transcriptional gene silencing systems. Owing to its ability to compare the genomes of two mating partners, MSUD represents a defense system for the maintenance of genome integrity as well as a possible isolation mechanism for speciation. N. crassa is an excellent model organism to assess the process of meiotic silencing because of its superior genetics and mutant selection, the ease of molecular techniques, and the availability of full genome sequence information. Genetics, cell biology, and other approaches will be used to identify the machinery and the mechanistic steps required for the meiotic silencing system. The study of MSUD in N. crassa will provide an excellent model for the delineation of the mechanism targeting unpaired DNA for silencing during meiosis, a process that could be important for imprinted X-chromosome inactivation and numerous other phenomena. Since RNAi has tremendous potential as an experimental tool to reveal gene functions, the understanding of MSUD and other RNA-based silencing systems could have a broad impact on research in all areas of biology. Furthermore, the P.I. is involved in a number of teaching and mentoring activities and is registered as a mentor for the Ronald McNair Scholars Program, which aims to promote graduate enrollment for underprivileged first-generation college students and members of underrepresented groups.