negative regulation of transcription by RNA polymerase I

Definition

Target type: biologicalprocess

Any process that stops, prevents, or reduces the frequency, rate or extent of transcription mediated by RNA polymerase I. [GOC:go_curators]

Negative regulation of transcription by RNA polymerase I is a complex process involving a variety of factors that act to suppress the production of ribosomal RNA (rRNA). rRNA is a key component of ribosomes, the cellular machinery responsible for protein synthesis. Therefore, regulating its production is essential for maintaining cellular homeostasis.

One of the primary mechanisms of negative regulation involves the binding of repressor proteins to specific DNA sequences within the rRNA gene promoter. These repressors can block the binding of transcription factors required for RNA polymerase I recruitment and initiation of transcription. Examples of such repressors include:

* **Upstream Binding Factor (UBF):** UBF is a key transcription factor for rRNA gene transcription, but its interaction with the promoter can be inhibited by other factors. For instance, the nucleolar protein **Nopp140** can bind to UBF and prevent it from activating transcription.

* **TIF-IA:** TIF-IA is another transcription factor essential for RNA polymerase I activity. Its activity is regulated by proteins like **SL1** (also known as TBP-associated factor 1), which can interact with TIF-IA and inhibit its function.

* **Other Repressors:** Additional repressors, such as **rRNA transcription termination factor 1 (TTF-1)** and **p53**, can also contribute to the negative regulation of RNA polymerase I transcription by blocking the initiation of transcription or promoting premature termination of transcription.

**Post-transcriptional regulation:** Beyond the transcriptional level, the production of rRNA can be controlled by mechanisms affecting the processing and stability of rRNA transcripts.

* **Ribosomal protein availability:** The availability of ribosomal proteins is critical for rRNA processing and ribosome assembly. When ribosomal protein levels are low, the production of rRNA may be reduced.

* **Nucleolar stress:** Stressful conditions, such as DNA damage or nutrient deprivation, can trigger a response that leads to the inhibition of rRNA synthesis. This can involve the phosphorylation and inactivation of transcription factors or the induction of specific microRNAs that target rRNA transcripts.

In summary, the negative regulation of transcription by RNA polymerase I involves a diverse array of mechanisms that ensure proper control of rRNA production. These mechanisms are tightly regulated and can be influenced by various cellular signals and stressors, ultimately contributing to the overall balance and function of the cell.'
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Proteins (2)

Compounds (30)