repressor

Examples of repressor in the following topics:

• The trp Operon: A Repressor Operon

  • The trp operon is a repressor operon that is either activated or repressed based on the levels of tryptophan in the environment.
  • This operator contains the DNA code to which the repressor protein can bind.
  • When tryptophan is plentiful, two tryptophan molecules bind the repressor protein at the operator sequence.
  • When tryptophan is absent, the repressor protein does not bind to the operator and the genes are transcribed.
  • Explain the relationship between structure and function of an operon and the ways in which repressors regulate gene expression

• Transcriptional Enhancers and Repressors

  • Enhancers increase the rate of transcription of genes, while repressors decrease the rate of transcription.
  • Transcriptional repressors can bind to promoter or enhancer regions and block transcription.
  • Like the transcriptional activators, repressors respond to external stimuli to prevent the binding of activating transcription factors.

• RNA Splicing

  • Some of these regulatory proteins include splicing activators (proteins that promote certain splicing sites) and splicing repressors (proteins that reduce the use of certain sites).
  • Some common splicing repressors include: heterogeneous nuclear ribonucleoprotein (hnRNP) and polypyrimidine tract binding protein (PTB).
  • As noted above, splicing is regulated by repressor proteins and activator proteins, which are are also known as trans-acting proteins.

• Initiation of Transcription in Eukaryotes

  • Other proteins known as activators and repressors, along with any associated coactivators or corepressors, are responsible for modulating transcription rate.
  • Activator proteins increase the transcription rate, and repressor proteins decrease the transcription rate.

• The lac Operon: An Inducer Operon

  • If lactose is absent, then the repressor binds to the operator to prevent transcription.