概括
对于真核核糖酶体启动的最佳序列是ACCATGG. 这一发现来自于分析前胰岛素基因突变,增强了对翻译效率和启动密码子识别的理解.
科学领域:
- 分子生物学分子生物学
- 遗传学 是一个遗传学.
- 生物化学 生物化学
背景情况:
- 翻译启动是基因表达的一个关键步骤.
- 围绕启动器ATG编码子的序列会影响翻译效率.
- 以前的研究表明,对于真核细胞翻译启动的共识序列.
研究的目的:
- 为了确定优化核酸序列的真核糖核糖体启动.
- 调查单基替代在ATG密码子周围对蛋白质产量的影响.
- 了解侧边核酸在翻译启动和启动密码子选择中的作用.
主要方法:
- 一个克隆的人类前胰岛素基因的局部定向突变发生.
- 在启动者码头区域发生突变后对亲胰岛素产量的分析.
- 对上游ATG编码子对下游启动的影响的评估.
主要成果:
- 确定了序列ACCATGG作为最佳的翻译启动.
- 在这个最佳序列中的突变改变了多达20倍的亲胰岛素产量.
- 处于位置-3的纯素显著影响启动效率,而pyrimidines增加了对其他位置的敏感性.
- 上游ATG编码子可以作为下游启动的障碍.
结论:
- 确定的最佳启动序列 (ACCATGG) 与以前观察到的真核mRNA的共识序列相匹配.
- 在调节翻译效率方面,围绕ATG启动子的核酸背景起着至关重要的作用.
- 了解这些序列可以为控制基因表达的策略提供信息.
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Mutations
Overview
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Overview
Initiation of Translation
Initiating translation is complex because it involves multiple molecules. Initiator tRNA, ribosomal subunits, and eukaryotic initiation factors (eIFs) are all required to assemble on the initiation codon of mRNA. This process consists of several steps that are mediated by different eIFs.
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
First, the initiator tRNA must be selected from the pool of elongator tRNAs by eukaryotic initiation factor 2 (eIF2). The initiator tRNA (Met-tRNAi) has conserved sequence elements including modified bases at...
Leaky Scanning
During most eukaryotic translation processes, the small 40S ribosome subunit scans an mRNA from its 5' end until it encounters the first start AUG codon. The large 60S ribosomal subunit then joins the smaller one to initiate protein synthesis. The location of the translation initiation is largely determined by the nucleotides near the start codon as there may be multiple translation initiation sites present on the mRNA. Marilyn Kozak discovered that the sequence RCCAUGG (where R stands for...
Mutations
Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. Mutations can be characterized in a number of different ways: whether and how they alter the amino acid sequence of the protein, whether they occur over a small or large area of DNA, and whether they occur in somatic cells or germline cells.
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Chromosomal Alterations Are Large-Scale Mutations
While point mutations are changes in a single nucleotide in...
Point and Frameshift Mutations
Point mutations are genetic alterations involving the change of a single nucleotide base pair in DNA. Depending on how the alteration affects protein synthesis, they can lead to various consequences.Point mutations fall into the following types:Silent mutations occur when a nucleotide change does not alter the amino acid sequence due to the redundancy of the genetic code. For instance, changing ACC to ACA still encodes threonine, leaving the protein function unaffected. This occurs because...
