transcriptional attenuation

Definition

Target type: biologicalprocess

A negative regulation of gene expression mechanism by which bacteria and archae can direct RNA polymerase to prematurely terminate transcription in response to a specific metabolic signal. [PMID:12210530, PMID:15851059, PMID:7007895]

Transcriptional attenuation is a regulatory mechanism that controls gene expression at the level of transcription termination. It occurs in prokaryotes and involves premature termination of transcription before the gene of interest is fully transcribed. The process is often used to regulate the expression of genes involved in amino acid biosynthesis. Here’s a detailed description of how it works:

1. **Leader Sequence:** The DNA sequence upstream of the gene of interest contains a regulatory region known as the leader sequence. This sequence has two important features:
* **Ribosome Binding Site (RBS):** A sequence that allows ribosomes to bind and initiate translation.
* **Attenuator Region:** A region containing a series of short sequences that can form alternative stem-loop structures.

2. **Transcription and Translation Coupling:** In prokaryotes, transcription and translation are coupled processes. As the RNA polymerase transcribes the leader sequence, ribosomes bind to the RBS and begin translating the leader mRNA.

3. **Alternative Stem-Loop Structures:** The attenuator region of the leader sequence contains four short sequences that can form alternative stem-loop structures. These structures are influenced by the presence or absence of the amino acid that the gene is responsible for producing.

4. **Attenuation Mechanism:**
* **Abundant Amino Acid:** If the amino acid is abundant, ribosomes translate through the leader sequence without pausing. This allows the formation of a stem-loop structure that terminates transcription prematurely.
* **Limited Amino Acid:** If the amino acid is scarce, ribosomes stall at a specific codon within the leader sequence. This stalling allows a different stem-loop structure to form, which does not terminate transcription.

5. **Transcription Termination:** The formation of the terminator stem-loop structure signals RNA polymerase to dissociate from the DNA template, preventing further transcription of the gene.

In essence, transcriptional attenuation acts as a feedback mechanism. When the amino acid is abundant, transcription is terminated, preventing the synthesis of more of that amino acid. When the amino acid is scarce, transcription continues, allowing for the production of more of the amino acid. This process ensures that cells only produce the necessary amounts of specific amino acids, preventing wasteful overproduction.'
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Proteins (1)

Compounds (21)