positive regulation of transcription by RNA polymerase III

Definition

Target type: biologicalprocess

Any process that activates or increases the frequency, rate or extent of transcription mediated by RNA polymerase III. [GOC:go_curators, GOC:txnOH]

Positive regulation of transcription by RNA polymerase III is a complex and essential process that controls the synthesis of a wide variety of small, non-coding RNAs. These RNAs play crucial roles in a multitude of cellular functions, including translation, ribosome biogenesis, and RNA processing. The process involves the coordinated action of numerous factors, including transcription factors, coactivators, and chromatin modifiers.

Transcription initiation by RNA polymerase III is distinct from that of RNA polymerase II, which transcribes protein-coding genes. RNA polymerase III promoters are typically located within the transcribed region of the gene, rather than upstream of it. They often contain internal control regions (ICRs), which are short sequence elements that bind specific transcription factors.

The process can be broadly divided into the following steps:

1. **Transcription Factor Binding**: Specific transcription factors, such as TFIIIA, TFIIIB, and TFIIIC, recognize and bind to the ICRs within the gene. TFIIIA binds to the 5S rRNA gene, while TFIIIB and TFIIIC bind to the tRNA gene.

2. **Assembly of the Transcription Pre-initiation Complex (PIC)**: The transcription factors bind to the DNA, forming a stable complex that recruits RNA polymerase III. This complex is referred to as the PIC.

3. **Recruitment of RNA Polymerase III**: Once the PIC is formed, RNA polymerase III is recruited to the promoter, facilitated by the interactions between TFIIIB and the polymerase.

4. **Initiation of Transcription**: RNA polymerase III initiates transcription at the start site within the promoter, producing a primary transcript.

5. **Elongation and Termination**: RNA polymerase III then transcribes the gene, elongating the RNA molecule. The process is terminated at specific termination signals, releasing the newly synthesized RNA transcript.

6. **Post-Transcriptional Modifications**: The newly transcribed RNA may undergo further processing, including capping, splicing, and polyadenylation, depending on the specific type of RNA.

The positive regulation of transcription by RNA polymerase III is tightly controlled by a variety of mechanisms, including:

* **Signal-dependent activation**: In response to various cellular signals, specific transcription factors are activated, promoting the assembly of the PIC and subsequent transcription.

* **Chromatin Remodeling**: Chromatin modifications, such as histone acetylation and methylation, can influence the accessibility of the DNA to transcription factors and RNA polymerase III.

* **Post-translational modifications of transcription factors**: Modifications of transcription factors, such as phosphorylation and acetylation, can alter their activity and influence the transcription process.

* **Interaction with other cellular factors**: Transcription factors and RNA polymerase III can interact with other cellular proteins and complexes, further regulating their activity and influencing transcription.

The positive regulation of transcription by RNA polymerase III is a complex and dynamic process that is crucial for maintaining cellular homeostasis and proper gene expression. It involves a precise interplay of various factors and regulatory mechanisms, ensuring the accurate production of essential non-coding RNAs that support diverse cellular functions.
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Proteins (3)

Compounds (231)