Chapter 15 - Gene regulation in Eukaryotes I: Transcriptional and
Translation Regulation.
15.1 Regulatory Transcription Factors
The term transcription factor is broadly used to describe a category of proteins that influence
the ability of RNA polymerase to transcribe a given gene. The general transcription factors
are required for the binding of RNA polymerase to the core promoter and its progression to
the elongation stage. In addition, eukaryotic cells possess a diverse array of regulatory
transcription factors that serve to regulate the rate of transcription of target genes.
The DNA sequences are generally known as control elements, regulatory elements or
regulatory sequences.
- Activator binds to an enhancer
- Repressor binds to a silencer
Combinatorial control is the phenomenon that genes are regulated by many factors.
Structural features of regulatory transcription factors allow the to bind to DNA.
Domains are regions of proteins which have a specific function. When a domain or portion of
a domain has a very similar structure in many different proteins, the structurally similar
region is called a motif. The α-helix is frequently occuring in transcription factors, because it
has a proper width to bind into the major groove of the DNA double helix.
Two identical transcription factors may come together to form a homodimer, or two different
transcription factors can form a heterodimer.
Certain motifs promote protein dimerization. The leucine zipper and helix-loop-helix motif
both promote that.
The zinc finger motif can recognize DNA sequences within the major groove.
Regulatory transcription factors recognize regulatory elements that function as
enhancers or silencers. Enhancers serve to increase transcription, and their action is
called up regulation. Silencers serve to inhibit transcription, and their action is called down
regulation. Many regulatory elements are orientation-independent, or bidirectional. This
means that the regulatory elements functions in the forward or reverse direction.
Regulatory transcription factors may exert their effects through TFIID and mediator.
- Regulation via TFIID
- Activator proteins can enhance the ability of TFIID to initiate transcription. It
might help to bind to the TATA box or they might enhance the function of
TFIID in way that facilitates its ability to recruit RNA polymerase II. Activator
proteins exert their effects by interacting with coactivators, proteins that
increase the rate of transcription but do not directly bind to DNA itself.
- Coactivators typically contain a transactivation domain that promotes the
activation of RNA polymerase, often by interacting with general transcription
factors.
- Repressors inhibit the function of TFIID. They could exert their effects by
preventing the binding to the TATA box or by inhibiting the ability of TFIID to
recruit to the core promoter.
- Regulation via mediator
- A mediator mediates the interaction between RNA polymerase II and
Translation Regulation.
15.1 Regulatory Transcription Factors
The term transcription factor is broadly used to describe a category of proteins that influence
the ability of RNA polymerase to transcribe a given gene. The general transcription factors
are required for the binding of RNA polymerase to the core promoter and its progression to
the elongation stage. In addition, eukaryotic cells possess a diverse array of regulatory
transcription factors that serve to regulate the rate of transcription of target genes.
The DNA sequences are generally known as control elements, regulatory elements or
regulatory sequences.
- Activator binds to an enhancer
- Repressor binds to a silencer
Combinatorial control is the phenomenon that genes are regulated by many factors.
Structural features of regulatory transcription factors allow the to bind to DNA.
Domains are regions of proteins which have a specific function. When a domain or portion of
a domain has a very similar structure in many different proteins, the structurally similar
region is called a motif. The α-helix is frequently occuring in transcription factors, because it
has a proper width to bind into the major groove of the DNA double helix.
Two identical transcription factors may come together to form a homodimer, or two different
transcription factors can form a heterodimer.
Certain motifs promote protein dimerization. The leucine zipper and helix-loop-helix motif
both promote that.
The zinc finger motif can recognize DNA sequences within the major groove.
Regulatory transcription factors recognize regulatory elements that function as
enhancers or silencers. Enhancers serve to increase transcription, and their action is
called up regulation. Silencers serve to inhibit transcription, and their action is called down
regulation. Many regulatory elements are orientation-independent, or bidirectional. This
means that the regulatory elements functions in the forward or reverse direction.
Regulatory transcription factors may exert their effects through TFIID and mediator.
- Regulation via TFIID
- Activator proteins can enhance the ability of TFIID to initiate transcription. It
might help to bind to the TATA box or they might enhance the function of
TFIID in way that facilitates its ability to recruit RNA polymerase II. Activator
proteins exert their effects by interacting with coactivators, proteins that
increase the rate of transcription but do not directly bind to DNA itself.
- Coactivators typically contain a transactivation domain that promotes the
activation of RNA polymerase, often by interacting with general transcription
factors.
- Repressors inhibit the function of TFIID. They could exert their effects by
preventing the binding to the TATA box or by inhibiting the ability of TFIID to
recruit to the core promoter.
- Regulation via mediator
- A mediator mediates the interaction between RNA polymerase II and
