uORF-mediated Translational Control of Cardiac Transcription Factor Expression

信使核糖核酸(MRNA)的5‘非翻译区中的短肽编码序列， 被称为上游开放阅读框架(UORF)的基因广泛存在于约50%的人类mRNAs中。翻译 这些uORF序列减少了mRNA主开放阅读框架(Morf)的蛋白质输出。我们的 人和小鼠核糖体图谱数据库的生物信息学分析揭示了一组心脏 包含翻译的uORF的mRNA转录本，如转录因子，包括GATA4。 生化分析表明，稳定下游的双链RNA(DsRNA)结构 这些肽编码序列的起始密码子增强了它们的翻译，从而抑制了 莫尔夫的翻译。这种翻译抑制机制被死盒RNA解旋酶缓解。 解开dsRNA并使uORF失活的DDX3X。GATA4 uORF活性的遗传耗竭 CRISPR-Cas9介导的人类胚胎干细胞起始密码子的基因组编辑提供了 UORF介导的Morf翻译调节和心肌细胞肥大的证据。在……里面 此外，建立的CRISPR-Cas9衍生的uORF起始密码子突变敲入小鼠模型显示 自发性心肌肥厚，将被用来描述基线及以下的心肌肥厚 压力条件。基于我们发现的DDX3X调控、dsRNA依赖、 UORF介导的Morf的翻译抑制，我们开发了两种类型的反义 寡核苷酸(ASO)可通过增强或干扰uORF的翻译来增强或减少uORF的翻译 DsRNA结构。UORF增强的ASO锁定dsRNA结构并激活 UORF，从而降低人CMS中GATA4 Morf蛋白的表达。对小白鼠的治疗 UORF增强的ASO心肌病模型降低GATA4蛋白表达，拮抗 心脏肥大，恢复心脏功能。根据我们的发现，我们假设心脏 转录因子mRNA uORF-dsRNA元件作为Morf翻译调控的开关， 调节心肌肥厚，并可被ASOS靶向调节Morf蛋白的翻译和 心肌肥厚。我们将重点关注3个具体目标。目的1.阐明信使核糖核酸的结构元件和 它们与GATA4 uORF相互作用，调节Morf翻译。目标2.确定生物角色 在基因敲入小鼠模型和原代CM细胞培养系统中GATA4 uORF的表达。目标3. 开发针对GATA4 uORF的概念验证翻译操纵ASO，用于短期反 肥大干预。这些研究将为翻译控制机制提供新的见解 在心脏生物学方面。该项目将促进新的治疗方法(针对uORF-dsRNA 元素)来调节心肌肥厚。我们基于机构的平移操作设计 ASOS可以作为一个概念验证模型来应用于不同的致病基因靶点。

Short peptide-encoding sequences in the 5' untranslated region of messenger ribonucleic acids (mRNA), called upstream open reading frames (uORFs), are widespread in ~50% of human mRNAs. Translating these uORF sequences reduces the protein output of an mRNA main open reading frame (mORF). Our bioinformatic analysis of human and mouse ribosome profiling databases uncovered a group of cardiac mRNA transcripts containing translated uORFs, such as transcription factors, including GATA4. Biochemical analysis suggests that stabilizing the double-stranded RNA (dsRNA) structure downstream of the start codons of these peptide-encoding sequences enhances their translation, thereby inhibiting the translation of mORFs. This translational inhibitory mechanism is mitigated by DEAD-box RNA helicase DDX3X that unwinds dsRNA and inactivates uORF. Genetic depletion of GATA4 uORF activity using CRISPR-Cas9 mediated genomic editing of the start codon in human embryonic stem cells (ESC) provides evidence of uORF-mediated regulation of mORF translation and cardiomyocyte (CM) hypertrophy. In addition, an established CRISPR-Cas9-derived uORF start codon mutant knock-in mouse model shows spontaneous cardiac hypertrophy and will be used to characterize CM hypertrophy at baseline and under stress conditions. Based on our discovered molecular mechanism of DDX3X-regulated, dsRNA-dependent, uORF-mediated translational inhibition of mORF, we have developed two types of antisense oligonucleotides (ASOs) that can either enhance or reduce uORF translation by strengthening or disrupting dsRNA structures. The uORF-enhancing ASO locks the dsRNA structure and activates translation of the uORF, thereby reducing GATA4 mORF protein expression in human CMs. Treatment of mouse cardiomyopathy models with uORF-enhancing ASO reduces GATA4 protein expression, antagonizes cardiac hypertrophy, and restores cardiac function. Based on our findings, we hypothesize that cardiac transcription factor mRNA uORF-dsRNA element acts as a switch for translational control of mORF, regulating cardiac hypertrophy, and can be targeted by ASOs to modulate mORF protein translation and cardiac hypertrophy. We will focus on 3 Specific Aims. Aim 1. Elucidate mRNA structural elements and their interplay with the GATA4 uORF for regulating mORF translation. Aim 2. Determine the biological role of the GATA4 uORF in genetic knock-in mouse models and primary CM cell culture systems. Aim 3. Develop proof-of-concept translation-manipulating ASOs targeting the GATA4 uORF for short-term anti- hypertrophy intervention. These studies will provide novel insights into translational control mechanisms in cardiac biology. This project will promote novel therapeutic approaches (targeting uORF-dsRNA elements) to regulate cardiac hypertrophy. Our mechanism-based design of translation-manipulating ASOs can serve as a proof-of-concept model to apply to different pathogenic mRNA targets.