Biological functions and post-transcriptional regulation of microRNAs

MicroRNAs(MiRNAs)是一种小的非编码RNAs，它被装载到ArgAerte蛋白中，形成miRNA诱导沉默复合体(MiRISC)的核心。MiRNAs引导miRISC与互补的靶mRNAs结合，使其表达沉默。MiRNA基因座的突变扰乱了基因表达程序，从而可能导致包括癌症在内的各种疾病的发展。因此，了解miRNAs在正常发育中的功能和调节miRNAs的分子机制都是至关重要的生物学问题。 了解miRNAs在胚胎发育过程中的生物学功能 虽然在线虫和其他生物中对miRNAs在分化组织中的功能进行了很好的研究，但只有少数动物的miRNAs的胚胎功能被了解。线虫是研究胚胎发育的良好模式生物，因为它有明确的定型细胞谱系和强大的遗传工具。我们正在对microRNA家族突变表型的抑制者进行正向(突变)和反向(RNAi)筛选，目前重点放在高度保守的mir-51家族上。我们还利用CRISPR-Cas9介导的基因组编辑的力量来发现对发育至关重要的miRNA-目标相互作用(Yang等人。2020)。了解受胚胎表达的microRNA家族影响的生物网络将为如何控制基因表达以协调胚胎发生提供重要的见解。 确定miRNA和ArgAerte周转的分子机制 MiRNA生物发生和衰退速率的平衡控制miRNA的丰度，从而控制基因表达程序。以前的研究已经仔细地阐明了miRNA生物发生的机制。然而，我们对miRNAs和miRISC是如何被结构性地或以受监管的方式移交的知之甚少。这是我们对miRNA调控，从而对基因表达调控的理解的一个主要差距。我们先前证明咖啡因诱导的死亡(CID-1)是miRNAs尿苷基化所必需的，而F31C3.2(我们命名为GLD-2相关-2)是miRNAs腺基化所必需的(Vieux等人)。2021年)。我们还发现，这些末端修饰在影响miRNA衰减率方面并不起到全局作用。最近，我们正在研究mir-35家族的受控衰退，该家族对胚胎发育至关重要，此后急剧下调。今年，我们证明了这个miRNA家族的衰退取决于它的种子序列(核苷酸2-8)，而不是miRNA序列的其他部分(Donnelly，等人)。2022年)。这代表了一种新的miRNA衰变机制，可以在治疗上利用这种机制来同时调节miRNA种子家族所有冗余成员的丰度。

MicroRNAs (miRNAs) are small noncoding RNAs that are loaded into Argonaute proteins to form the core of the miRNA-Induced Silencing Complex (miRISC). MiRNAs guide miRISC to complementary target mRNAs to silence their expression. Mutations in miRNA loci disrupt gene expression programs, and thus can contribute to the development of various diseases, including cancer. Consequently, understanding both the functions of miRNAs in normal development and the molecular mechanisms that regulate miRNAs are biological questions of critical importance. Understanding the biological functions of miRNAs during embryogenesis While the functions of miRNAs in differentiated tissues are well-studied in C. elegans and other organisms, the embryonic functions of only a few animal miRNAs are understood. C. elegans is an excellent model organism in which to study embryonic development due to its well-defined stereotypic cell lineage and powerful genetic tools. We are conducting forward (mutagenesis) and reverse (RNAi) screens for suppressors of microRNA family mutant phenotypes, currently focusing on the deeply conserved mir-51 family. We are also leveraging the power of CRISPR-Cas9-mediated genome editing to discover miRNA-target interactions that are essential to development (Yang, et al. 2020). Understanding the biological networks impacted by the embryonically-expressed microRNA families will yield important insights into how gene expression is controlled to coordinate embryogenesis. Defining the molecular mechanisms of miRNA and Argonaute turnover The balance of the rates of miRNA biogenesis and decay control miRNA abundance, and thus gene expression programs. Previous research has carefully elucidated mechanisms of miRNA biogenesis. However, we know very little about how miRNAs and miRISC are turned over either constitutively or in a regulated manner. This is a major gap in our understanding of miRNA regulation, and thus the regulation of gene expression. We previously demonstrated that Caffeine-Induced Death (CID-1) is necessary for uridylation of miRNAs, and F31C3.2 (which we named GLD-2 Related-2) is required for adenylation of miRNAs (Vieux, et al. 2021). We also found that these terminal modifications do not play a global role in influencing miRNA decay rates. More recently, we are investigating the regulated decay of the mir-35 family, which is essential for embryogenesis and sharply downregulated thereafter. This year, we showed that this miRNA familys decay is dependent upon its seed sequence (nucleotides 2-8), but not other parts of the miRNA sequence (Donnelly, et al. 2022). This represents a novel class of miRNA decay mechanism that may be harnessed therapeutically to modulate abundance of all redundant members of a miRNA seed family simultaneously.