Transcriptional repressors

Definition

Transcriptional repressors are proteins that bind to specific DNA sequences and inhibit the transcription of genes, effectively reducing or silencing gene expression. By interacting with promoter regions or enhancer elements, these repressors prevent the recruitment of RNA polymerase and other transcription factors necessary for initiating transcription, thus playing a critical role in gene regulation in eukaryotic cells.

5 Must Know Facts For Your Next Test

1. Transcriptional repressors can work through several mechanisms, including competitive binding to DNA sites or recruiting co-repressors that modify chromatin structure to inhibit access to the DNA.
2. Some well-known transcriptional repressors include the protein complex known as REST, which represses neuronal genes in non-neuronal tissues.
3. Repressors can be tissue-specific, meaning they may only act in certain cell types or developmental stages, allowing for precise regulation of gene expression.
4. Environmental signals can influence the activity of transcriptional repressors, leading to changes in gene expression in response to different stimuli.
5. Dysregulation of transcriptional repressors has been linked to various diseases, including cancer and genetic disorders, highlighting their importance in maintaining normal cellular function.

Review Questions

• How do transcriptional repressors interact with DNA to regulate gene expression?
  • Transcriptional repressors interact with specific DNA sequences either within promoter regions or nearby enhancers. They bind to these sites and inhibit the recruitment of RNA polymerase and necessary transcription factors needed for gene activation. This binding can block the formation of the transcription initiation complex or interfere with enhancer-promoter interactions, ultimately leading to reduced gene expression.
• Compare and contrast the roles of transcriptional repressors and activators in eukaryotic gene regulation.
  • Transcriptional repressors and activators serve opposing roles in regulating gene expression. While repressors inhibit transcription by binding to DNA and blocking necessary components from accessing genes, activators enhance transcription by promoting the assembly of the transcription initiation complex at promoters. Both types of factors interact with the same basic machinery but work in opposite directions to fine-tune gene expression based on cellular needs and environmental signals.
• Evaluate how changes in environmental signals might affect the function of transcriptional repressors and consequently impact cellular processes.
  • Changes in environmental signals can significantly affect the function of transcriptional repressors by altering their binding affinity or activity. For example, a stress signal may lead to post-translational modifications that change how a repressor interacts with its target DNA. This alteration could lead to either increased repression or derepression of certain genes. Consequently, such changes can impact various cellular processes like differentiation, metabolism, and responses to stress, reflecting how dynamic and responsive gene regulation is to external stimuli.

Related terms

Enhancers: DNA sequences that, when bound by specific proteins, increase the likelihood of transcription of a particular gene, often working in conjunction with promoters.

Silencers: Regions of DNA that, when bound by repressor proteins, can silence the expression of nearby genes by preventing transcription.

Transcription Factors:

Proteins that help regulate the transcription of specific genes by binding to nearby DNA, including both activators that enhance transcription and repressors that inhibit it.