transcription antitermination

Definition

Target type: biologicalprocess

A positive regulation of gene expression mechanism that allows RNA polymerase to continue transcription beyond a termination site, thus allowing expression of downstream genes under specific conditions. [ISBN:0198577788, PMID:12456320, PMID:21478900, PMID:30191803]

Transcription antitermination is a biological process that allows RNA polymerase to continue transcribing a gene beyond a termination signal. This process is essential for the expression of many genes, particularly those involved in stress response, virulence, and phage infection.

Typically, transcription termination occurs when RNA polymerase encounters a termination signal in the DNA sequence. This signal often consists of a GC-rich sequence followed by a run of adenines (poly-A tract). The poly-A tract causes the RNA polymerase to pause and dissociate from the DNA, releasing the newly synthesized RNA molecule.

However, in some cases, the RNA polymerase is prevented from terminating transcription. This can occur due to the presence of antitermination factors, which are proteins that bind to the RNA polymerase and prevent it from dissociating. Antitermination factors often recognize specific sequences in the RNA molecule that are downstream of the termination signal.

There are two main mechanisms of antitermination:

1. **Binding to the RNA polymerase:** Some antitermination factors bind directly to the RNA polymerase and prevent it from pausing or dissociating. An example of this is the N protein of phage lambda. The N protein binds to the RNA polymerase and prevents it from pausing at a specific termination site, allowing transcription to continue through the entire operon.

2. **Binding to the RNA molecule:** Other antitermination factors bind to specific sequences in the RNA molecule downstream of the termination signal. This binding can alter the structure of the RNA molecule, making it less likely to be recognized by the termination signal. A good example is the Q protein of phage lambda. The Q protein binds to a specific sequence in the RNA molecule and causes a conformational change that prevents the formation of a hairpin loop, which is required for termination.

Antitermination is a highly regulated process. The expression of antitermination factors is often controlled by environmental cues, such as stress or the presence of a phage. This allows cells to regulate the expression of genes that are needed only under specific conditions.

Antitermination is a vital process in many biological systems. It allows for the coordinated expression of genes that are essential for a variety of functions, including stress response, virulence, and phage infection. By preventing termination, antitermination factors ensure that these genes are transcribed and translated, enabling the organism to respond appropriately to its environment.'
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Proteins (8)

Compounds (23)