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相关概念视频

pre-mRNA Processing02:01

pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...
Pre-mRNA Processing02:01

Pre-mRNA Processing

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is replaced by modified guanosine that has a methyl group attached to it (7-Methyl guanosine). This 5’ cap helps the...
Transfer RNA Synthesis02:36

Transfer RNA Synthesis

One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
Pre-mRNA Processing: Modification of pre-mRNA Ends01:35

Pre-mRNA Processing: Modification of pre-mRNA Ends

In eukaryotic cells, transcripts made by RNA polymerase are modified and processed before exiting the nucleus. Unprocessed RNA is called precursor mRNA or pre-mRNA to distinguish it from mature mRNA.
Once about 20-40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes adds a cap to the 5' end of the growing transcript. In this process, a 5' phosphate is replaced by modified guanosine that has a methyl group attached (7-methyl guanosine). This 5' cap helps the cell...
Transfer RNA Synthesis02:36

Transfer RNA Synthesis

One of the unique features of tRNA is the presence of modified bases. In some tRNAs, modified bases account for nearly 20% of the total bases in the molecule. Altogether, these unusual bases protect the tRNA from enzymatic degradation by RNases.
Each of these chemical modifications is carried by a specific enzyme, post-transcription. All of these enzymes have unique base and site-specificity. Methylation, the most common chemical modification, is carried by at least nine different enzymes, with...
Nucleic Acid Structure01:25

Nucleic Acid Structure

The pentose sugar in DNA is deoxyribose, while in RNA the pentose sugar is ribose. The difference between the sugars is the presence of the hydroxyl group on the ribose's second carbon and a hydrogen on the deoxyribose's second carbon. The phosphate residue attaches to the hydroxyl group of the 5′ carbon of one sugar and the hydroxyl group of the 3′ carbon of the sugar of the next nucleotide, which forms  a 5′ to 3′ phosphodiester linkage.
DNA Structure
DNA has a double-helix structure. The...

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相关实验视频

Updated: Jul 22, 2026

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro
09:16

Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

Published on: May 3, 2014

细胞前tRNA 5'处理核酶:与复杂的圆柱形粒子共净化.

J G Castaño, R Ornberg, J G Koster

    Cell
    |August 1, 1986
    PubMed
    概括

    研究人员描述了一种真核前体转移RNA (tRNA前体) 5'处理内核酶的结构. 这种酶是从Xenopus laevis的卵巢中分离出来的,存在于一个大型复合体中,这表明在真核生物中存在着保存的机制.

    科学领域:

    • 分子生物学分子生物学
    • 结构生物学 结构生物学
    • 生物化学 生物化学

    背景情况:

    • 细胞前体转移RNA (tRNA前体) 分子经由特定的内核酶进行5'端处理.
    • 这种关键酶的结构细节在很大程度上仍然没有被描述.
    • 了解这种处理对于tRNA成熟和基因表达调节至关重要.

    研究的目的:

    • 描述一个真核细胞前tRNA5'处理内核酶的结构.
    • 为了阐明这种酶复合物的分子组成和组织.
    • 要确定特征化的酶是否代表了真核核酶的一般类.

    主要方法:

    • 从Xenopus laevis的卵巢中分离和净化5'前tRNAase.
    • 复合净化分析以识别相关蛋白质和复合形成.
    • 宏分子复合体的生物化学表征.

    主要成果:

    • 从X. laevis卵巢中分离了5'前tRNAase,并发现它与16S宏分子复合体共净化.
    • 这个复合体包括至少14种不同的多,其分子重量在20,000至32,000之间.
    • 聚酸形成一个圆柱状的粒子,组织成四个环的堆,类似于之前描述的无处不在的真核细胞亚细胞粒子.

    更多相关视频

    Single-step Purification of Macromolecular Complexes Using RNA Attached to Biotin and a Photo-cleavable Linker
    08:12

    Single-step Purification of Macromolecular Complexes Using RNA Attached to Biotin and a Photo-cleavable Linker

    Published on: January 3, 2019

    Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
    10:59

    Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events

    Published on: May 13, 2019

    相关实验视频

    Last Updated: Jul 22, 2026

    Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro
    09:16

    Analysis of RNA Processing Reactions Using Cell Free Systems: 3' End Cleavage of Pre-mRNA Substrates in vitro

    Published on: May 3, 2014

    Single-step Purification of Macromolecular Complexes Using RNA Attached to Biotin and a Photo-cleavable Linker
    08:12

    Single-step Purification of Macromolecular Complexes Using RNA Attached to Biotin and a Photo-cleavable Linker

    Published on: January 3, 2019

    Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events
    10:59

    Artificial RNA Polymerase II Elongation Complexes for Dissecting Co-transcriptional RNA Processing Events

    Published on: May 13, 2019

  • 对来自HeLa细胞的酶也观察到类似的共净化.

    • 结论:

    • 首次描述了真核细胞前tRNA 5'处理内核酶的结构.
    • 该酶存在于一个大型的多多复合体中,具有独特的环状结构.
    • 这些发现表明,Xenopus laevis酶是真核细胞前tRNA 5'处理核酶的一般类别的代表,表明跨物种的保护机制.