negative regulation of transcription initiation by RNA polymerase II

Definition

Target type: biologicalprocess

Any process that decreases the rate, frequency or extent of a process involved in starting transcription from an RNA polymerase II promoter. [GOC:dph, GOC:tb, GOC:txnOH]

Negative regulation of transcription initiation by RNA polymerase II is a complex process that involves a wide range of molecular mechanisms to control the expression of genes. This process is essential for maintaining cellular homeostasis and responding to various environmental cues. Here's a detailed description of the biological process:

**1. Transcriptional Repressors:**
- Specific proteins called transcriptional repressors bind to DNA sequences located near the promoter region of target genes. These sequences are often called repressor binding sites.
- Repressors can block the binding of RNA polymerase II to the promoter, preventing the initiation of transcription.

**2. Chromatin Remodeling:**
- The DNA in eukaryotic cells is packaged into chromatin, a complex of DNA and proteins. The structure of chromatin can influence the accessibility of DNA to transcription factors and RNA polymerase II.
- Repressors can recruit chromatin remodeling complexes that alter the structure of chromatin, making the DNA less accessible. This can hinder the binding of RNA polymerase II and other factors necessary for transcription initiation.

**3. Histone Modifications:**
- Histones are proteins that associate with DNA to form nucleosomes, the basic units of chromatin.
- Repressors can recruit enzymes that modify histones by adding or removing specific chemical groups, such as acetyl, methyl, or phosphate groups.
- These modifications can alter the affinity of histones for DNA, making the DNA more or less accessible to transcription factors and RNA polymerase II.

**4. Co-repressor Complexes:**
- Repressors often interact with co-repressor complexes, which are multi-protein complexes that enhance the repressive activity of the repressor.
- These complexes can mediate various repressive mechanisms, such as chromatin remodeling, histone modifications, and recruitment of other repressors.

**5. Competition with Activators:**
- Repressors can compete with activators for binding to the promoter region of genes. Activators are proteins that enhance transcription by facilitating the recruitment of RNA polymerase II and other factors.
- Repressors can outcompete activators, preventing them from binding to the promoter and activating transcription.

**6. Signaling Pathways:**
- Repressors can be regulated by signaling pathways that respond to various environmental cues, such as stress, hormones, and nutrient availability.
- These signaling pathways can activate or inhibit repressors, allowing for rapid and dynamic regulation of gene expression.

**7. RNA Interference (RNAi):**
- In some cases, RNA interference (RNAi) can play a role in negative regulation of transcription initiation.
- Small RNA molecules, such as microRNAs (miRNAs), can bind to target messenger RNA (mRNA) molecules, preventing their translation into proteins.
- In some instances, miRNAs can also interact with specific proteins involved in transcription initiation, ultimately inhibiting the process.

**In summary, negative regulation of transcription initiation by RNA polymerase II is a multi-faceted process that involves a diverse array of molecular mechanisms. This intricate system allows for precise control of gene expression, ensuring that genes are only transcribed when and where they are needed.**'
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Proteins (2)

Compounds (10)