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Videos de Conceptos Relacionados

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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Video Experimental Relacionado

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

La nucleasa de procesamiento 5' del pre-ARNt eucariótico: copurificación con una partícula cilíndrica compleja.

J G Castaño, R Ornberg, J G Koster

    Cell
    |August 1, 1986
    PubMed
    Resumen

    Los investigadores caracterizaron la estructura de un precursor eucariótico de transferencia de ARN (pre-tRNA) 5' procesamiento de la endonucleasa. Esta enzima, aislada de los ovarios de Xenopus laevis, existe como un gran complejo, lo que sugiere un mecanismo conservado en los eucariotas.

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

    Published on: May 13, 2019

    Área de la Ciencia:

    • Biología Molecular Biología Molecular
    • Biología Estructural Biología estructural.
    • La bioquímica es la bioquímica.

    Sus antecedentes:

    • Las moléculas de ARN de transferencia de precursores eucariotas (pre-tRNA) se someten a un procesamiento del extremo 5' por una endonucleasa específica.
    • Los detalles estructurales de esta enzima crucial han permanecido en gran medida sin caracterizar.
    • Comprender este procesamiento es vital para la maduración del tRNA y la regulación de la expresión génica.

    Objetivo del estudio:

    • Para caracterizar la estructura de una endonucleasa de procesamiento 5' del pre-ARNt eucariota.
    • Para dilucidar la composición molecular y la organización de este complejo enzimático.
    • Determinar si la enzima caracterizada representa una clase general de nucleasas eucariotas.

    Principales métodos:

    • Aislamiento y purificación de la 5' pre-tRNAasa de los ovarios de Xenopus laevis.
    • Análisis de copurificación para identificar proteínas asociadas y formación de complejos.
    • Caracterización bioquímica del complejo macromolecular.

    Principales resultados:

    • Se aisló la 5' pre-tRNAasa de los ovarios de X. laevis y se encontró que copurificaba con un complejo macromolecular 16S.
    • Este complejo comprende al menos 14 polipéptidos distintos con pesos moleculares que van desde 20.000 hasta 32.000.
    • Los polipéptidos forman una partícula cilíndrica, organizada como una pila de cuatro anillos, que se asemeja a las partículas subcelulares eucariotas ubicuas descritas anteriormente.
    • Se observó una copurificación similar para la enzima de las células HeLa.

    Conclusiones:

    • Se ha caracterizado por primera vez la estructura de una endonucleasa procesadora 5' del pre-ARNt eucariota.
    • La enzima existe como un complejo polipéptido grande y múltiple con una estructura única en forma de anillo.
    • Los hallazgos sugieren que la enzima de Xenopus laevis es representativa de una clase general de nucleasas procesadoras eucariotas pre-tRNA 5', lo que indica un mecanismo conservado en todas las especies.