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Eukaryotic RNA Polymerases

Eukaryotic RNA Polymerases

RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
All three eukaryotic RNAPs require specific transcription factors, of which the...

Eukaryotic RNA Polymerases

Eukaryotic RNA Polymerases

RNA Polymerase (RNAP) is conserved in all animals, with bacterial, archaeal, and eukaryotic RNAPs sharing significant sequence, structural, and functional similarities. Among the three eukaryotic RNAPs, RNA Polymerase II is most similar to bacterial RNAP in terms of both structural organization and folding topologies of the enzyme subunits. However, these similarities are not reflected in their mechanism of action.
All three eukaryotic RNAPs require specific transcription factors, of which the...

Bacterial RNA Polymerase

Bacterial RNA Polymerase

Unlike eukaryotes, bacteria use a single RNA Polymerase (RNAP) to transcribe all genes. The different subunits of bacterial RNAPhave distinct functions. The multisubunit structure of the bacterial RNAP helps the enzyme to maintain catalytic function, facilitate assembly, interact with DNA and RNA, and self-regulate its activity.
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Bacterial RNA Polymerase

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The Replisome

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DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...

The Replisome

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DNA replication is carried out by a large complex of proteins that act in a coordinated matter to achieve high-fidelity DNA replication. Together this complex is known as the DNA replication machinery or the replisome.
The synthesis of the leading and lagging strands is a highly coordinated process. To explain this, the “Trombone model” was proposed by Bruce Alberts in 1980. The DNA loop formation starts when a primer is synthesized on the parent lagging strand. The loop grows with the...

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DNA-Tethered RNA Polymerase for Programmable In vitro Transcription and Molecular Computation

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ARN polimerasa I: es una máquina molecular multifuncional.

Jeremy R Haag¹, Craig S Pikaard

¹Department of Biology, Washington University, 1 Brookings Drive, St. Louis, MO, USA.

|December 28, 2007

Resumen

Los investigadores trazaron un mapa de la estructura de la ARN polimerasa I de la levadura utilizando microscopía criolectrónica. Esto reveló que tres subunidades manejan el alargamiento de la transcripción, a diferencia de los factores de transcripción utilizados por la ARN polimerasa II.

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Área de la Ciencia:

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

Sus antecedentes:

La ARN polimerasa I (Pol I) de la levadura es crucial para la síntesis del ARN ribosomal.
Comprender la estructura de Pol I es clave para descifrar su función en la transcripción.
Los datos estructurales anteriores para Pol I eran limitados, especialmente con respecto a sus interacciones de subunidad durante el alargamiento.

Objetivo del estudio:

Para determinar la estructura tridimensional completa de la enzima ARN polimerasa I de la levadura.
Para aclarar las funciones de las subunidades específicas en el alargamiento de la transcripción.
Para comparar los mecanismos funcionales de Pol I con el sistema relacionado de ARN polimerasa II (Pol II).

Principales métodos:

Se empleó la microscopía cryoelectrónica (cryo-EM) para obtener imágenes de alta resolución.
El estudio se centró en la enzima Pol I de levadura de 14 subunidades.
El procesamiento de imágenes y el modelado estructural se utilizaron para reconstruir la arquitectura de la enzima.

Principales resultados:

La estructura completa de la enzima Pol I de levadura de 14 subunidades se resolvió a una resolución de 12 Å.
Se identificaron tres subunidades específicas dentro de Pol I que desempeñan funciones clave en el alargamiento de la transcripción.
Estas funciones son intrínsecamente llevadas a cabo por las subunidades Pol I, a diferencia del sistema Pol II.

Conclusiones:

La estructura revela un mecanismo intrínseco para el alargamiento de la transcripción dentro de la levadura Pol I.
Esto pone de relieve una divergencia en los mecanismos funcionales entre los sistemas de ARN polimerasa I y II.
Los hallazgos proporcionan una base estructural para la comprensión de la transcripción génica del ARNr mediada por Pol I.