Transcription factor

Definition

A transcription factor is a protein that binds to specific DNA sequences, regulating the transcription of genetic information from DNA to messenger RNA. These proteins play a crucial role in gene expression, acting as molecular switches that can either activate or repress the transcription of target genes. By interacting with RNA polymerase and other components of the transcription machinery, transcription factors help control the timing and level of gene expression in response to various signals and conditions.

5 Must Know Facts For Your Next Test

1. Transcription factors can be classified into two main types: general transcription factors, which are necessary for the transcription of all protein-coding genes, and specific transcription factors, which regulate particular genes in response to cellular signals.
2. Many transcription factors are activated or inhibited by post-translational modifications, such as phosphorylation, which can affect their ability to bind to DNA and interact with other proteins.
3. The binding of transcription factors to enhancers can significantly increase the rate of transcription, often by looping the DNA to bring the enhancer in contact with the promoter region.
4. Some transcription factors function as repressors, preventing gene expression by blocking the binding of RNA polymerase or other activators to the promoter.
5. Transcription factors are crucial for processes like cell differentiation, development, and response to environmental changes, highlighting their importance in regulating gene expression.

Review Questions

• How do transcription factors interact with RNA polymerase during gene expression?
  • Transcription factors interact with RNA polymerase by binding to specific regions on DNA called promoters. Once bound, they can facilitate or inhibit the recruitment of RNA polymerase to initiate transcription. This interaction is crucial because it helps determine whether a gene is expressed or silenced, ultimately affecting protein production in the cell.
• Analyze the role of enhancers and their relationship with transcription factors in regulating gene expression.
  • Enhancers are regulatory DNA sequences that can significantly boost the transcription of a target gene. They work by binding specific transcription factors that facilitate the assembly of the transcriptional machinery at the promoter. This interaction often involves DNA looping, which brings enhancers into proximity with promoters, allowing for increased expression levels and fine-tuning of gene regulation based on cellular needs.
• Evaluate how changes in transcription factor activity can influence cellular responses to environmental signals.
  • Changes in transcription factor activity can dramatically alter how cells respond to environmental signals by modulating gene expression. For example, when a cell receives a stress signal, specific transcription factors may be activated or repressed through various mechanisms, including post-translational modifications. This can lead to rapid changes in protein synthesis that help the cell adapt to new conditions, highlighting the critical role these proteins play in maintaining cellular homeostasis and function.

Related terms

RNA polymerase:

An enzyme that synthesizes RNA from a DNA template during the process of transcription.

Promoter:

A specific region of DNA where RNA polymerase and transcription factors bind to initiate transcription of a gene.

Enhancer: A regulatory DNA sequence that can increase the likelihood of transcription of a particular gene by binding transcription factors.