RNA polymerase I general transcription initiation factor activity

Definition

Target type: molecularfunction

A general transcription initiation factor activity that contributes to transcription start site selection and transcription initiation of genes transcribed by RNA polymerase I. Factors required for RNA polymerase I transcription initiation include upstream activation factor (UAF), core factor (CF), TATA binding protein (TBP) and RRN3. In all species characterized, RNA polymerase I transcribes a large polycistronic transcript that is processed into several mature rRNAs (3 or 4 depending on the species), including the large subunit rRNA (28S in humans), the small subunit rRNA (18S in humans), as well as one or two additional smaller rRNAs (the 5.8S rRNA in humans). In most species, this large rRNA transcript is the sole product of RNA polymerase I. However there are rare exceptions, such as Trypanosoma brucei, where RNA polymerase I also transcribes certain mRNAs. [GOC:txnOH-2018, PMID:11500378, PMID:17972917, PMID:25346433, PMID:28340337, PMID:28842442, PMID:31358304]

RNA polymerase I (Pol I) general transcription initiation factor activity is essential for the transcription of ribosomal RNA (rRNA) genes, which encode the core components of ribosomes. These factors bind to the promoter region of rRNA genes and recruit Pol I to initiate transcription. The process involves multiple steps:

1. **Promoter Recognition and Binding:** The initiation factors recognize and bind to the core promoter elements within the rRNA gene, including the core promoter element (CPE) and the upstream control element (UCE).

2. **Assembly of the Preinitiation Complex (PIC):** The initiation factors, along with Pol I and other transcription factors, assemble into a multi-protein complex known as the preinitiation complex (PIC). The PIC forms a stable structure on the promoter, positioning Pol I for efficient transcription initiation.

3. **DNA Melting and Transcription Initiation:** The PIC facilitates DNA melting at the transcription start site, allowing Pol I to access the template strand. Pol I then initiates RNA synthesis using the template strand as a guide.

4. **Elongation and Termination:** After initiation, Pol I elongates the nascent rRNA transcript, moving along the DNA template. The elongation process involves the recruitment of additional factors that promote RNA synthesis and prevent premature termination.

5. **Processing and Maturation:** The newly synthesized rRNA transcript undergoes extensive processing and maturation steps, including cleavage, methylation, and base modification. These modifications are essential for the proper function of rRNA in ribosome assembly and protein synthesis.

The activity of RNA polymerase I general transcription initiation factors is tightly regulated to ensure the accurate and efficient synthesis of rRNA, which is crucial for cellular growth and development. Disruption of these factors can lead to defects in ribosome biogenesis and protein synthesis, ultimately contributing to various cellular dysfunctions.'
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Proteins (1)

Compounds (3)