DNA-templated transcription

Definition

Target type: biologicalprocess

The synthesis of an RNA transcript from a DNA template. [GOC:jl, GOC:txnOH]

DNA-templated transcription is a fundamental biological process that converts the genetic information encoded in DNA into RNA. It occurs in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells. This process involves a series of intricate steps, orchestrated by a complex machinery of enzymes and proteins:

1. **Initiation:** The process begins with the binding of RNA polymerase to the promoter region of a gene. The promoter is a specific DNA sequence that signals the start of transcription. RNA polymerase is an enzyme that catalyzes the synthesis of RNA using DNA as a template. In eukaryotes, RNA polymerase II is responsible for transcribing protein-coding genes.

2. **Elongation:** Once RNA polymerase is bound to the promoter, it unwinds a short segment of the DNA double helix. This unwinding exposes the template strand of DNA, which serves as the blueprint for RNA synthesis. RNA polymerase then moves along the template strand, reading the DNA sequence and adding complementary RNA nucleotides to the growing RNA chain. The RNA nucleotides are added one by one, following the base pairing rules: adenine (A) pairs with uracil (U), guanine (G) pairs with cytosine (C), and cytosine (C) with guanine (G).

3. **Termination:** Transcription ends when RNA polymerase reaches a specific DNA sequence called the terminator. The terminator signals the end of the gene and causes the RNA polymerase to detach from the DNA template. The newly synthesized RNA molecule, called messenger RNA (mRNA), is then released from the DNA template.

4. **Post-transcriptional processing:** In eukaryotic cells, the newly synthesized mRNA undergoes a series of modifications before it can be translated into a protein. These modifications include:
* **Capping:** A 5' cap is added to the 5' end of the mRNA molecule. This cap helps to protect the mRNA from degradation and facilitates its binding to ribosomes, the protein synthesis machinery.
* **Splicing:** Introns, non-coding regions within the mRNA, are removed and exons, coding regions, are joined together. This splicing process removes unnecessary information from the mRNA and ensures that only the coding regions are translated into protein.
* **Polyadenylation:** A poly(A) tail, a string of adenine nucleotides, is added to the 3' end of the mRNA molecule. This tail helps to stabilize the mRNA and protect it from degradation.

The mRNA molecule, now fully processed, exits the nucleus and enters the cytoplasm, where it can be translated into a protein. This translation process is another complex biological process that is essential for gene expression.'
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Proteins (16)

Compounds (551)