RNA polymerase II transcription repressor complex

Definition

Target type: cellularcomponent

A protein complex, located in the nucleus, that possesses activity that prevents or downregulates transcription from a RNA polymerase II promoter. [GOC:tb]

The RNA polymerase II transcription repressor complex is a multi-protein assembly that plays a crucial role in regulating gene expression by inhibiting the transcription of specific genes. This complex is composed of a diverse array of proteins, each contributing to its overall function. Key components include:

1. **Transcription factors:** These proteins directly bind to DNA sequences known as promoter regions, located upstream of the gene to be transcribed. They act as molecular switches, either facilitating or hindering the recruitment of RNA polymerase II, the enzyme responsible for transcribing DNA into RNA. Repressors within this complex bind to specific DNA sequences and block the binding of activator proteins, effectively preventing transcription initiation.

2. **Corepressors:** These proteins act as intermediaries, linking transcription factors to other components of the complex, facilitating the assembly and stabilization of the repressor machinery. They may also possess enzymatic activities, such as histone deacetylases (HDACs), that modify the chromatin structure, making DNA less accessible to RNA polymerase II.

3. **Chromatin-modifying enzymes:** These proteins directly alter the structure of chromatin, the complex of DNA and proteins that package genetic material within the nucleus. Repressor complexes often utilize histone deacetylases (HDACs) to remove acetyl groups from histone proteins, leading to a more condensed chromatin state. This condensation restricts access of RNA polymerase II to the DNA template, inhibiting transcription.

4. **Other regulatory proteins:** The complex can also include various other proteins that contribute to its overall function. These may include proteins involved in:

* **Signaling pathways:** Receiving signals from the cellular environment and relaying them to the repressor complex, enabling responsiveness to external cues.
* **Protein-protein interactions:** Stabilizing the complex and facilitating its interaction with other cellular components.

5. **DNA binding proteins:** These proteins specifically bind to DNA sequences within the promoter region or enhancers, acting as a physical barrier to RNA polymerase II binding. This binding can be direct or indirect, mediated by other proteins within the complex.

The precise composition of the RNA polymerase II transcription repressor complex can vary depending on the specific gene being regulated, the cellular context, and the signaling pathways involved. However, the general principle remains the same: these complexes act as molecular brakes, fine-tuning gene expression by preventing or inhibiting the transcription of specific genes.'
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Proteins (3)

Compounds (11)