Clear and orderly summary of Chapter 15 of the book "Genetics: Analysis and Principles, 6th Edition by Robert Brooker". Together with all my other summaries of Genetics I got an 8,5 for this course.
Genetics Summary Chapter 15 – Gene regulation in Eukaryotes I
Gene regulation can occur at many points during gene expression
Cells look different because of gene regulation. Some genes are expressed in nerve
cells for example and not in muscle cells.
Gene regulation necessary
- Expression of genes during various developmental stages of life cycle →
some only during embryonic other during adult
- Differences among distinct cell types → nerve / muscle cells
- Homeostasis → internal function in cell
- Optimal response to change nutrient availability, and environmental changes
and stresses
Regulatory transcription factors, chromatin remodeling and DNA methylation regulate
gene transcription
15.1 Regulatory Transcription Factors
Transcription factors; protein that influence ability of RNA polymerase to transcribe.
→ regulate the binding of transcriptional complex to the core promoter and/or control
switch from initiation to elongation stage
General transcription factors;
o General transcription factors; binding RNA pol to core promotor and its
progression to the elongation stage. Necessary for basal transcription
→ for any transcription
o Regulatory transcription factors; binds to a regulatory element and
influence the rate of transcription via RNA polymerase → for target
(doelwit) genes
Control elements/Regulatory element (sequence)/response
element/cis-acting; Regulatory transcription factor bind to
regulatory element, affects transcription of a gene.
- Enhancer → activator protein binds to enhancer →
gene activation
- Silencer → repressor protein binds to silencer →
gene inactivation
Combinatorial control; expression of gene is regulated by
variety of factors
Structural features of regulatory transcription factors
Domains; regions in transcription factor protein, which has specific function
Motif; domain has a very similar structure in different proteins
Transcription factors protein contain specific domains that involve variety of
processes.
- DNA binding function
- Provide binding site small effector
- Protein dimerization (production) → important way to modulate their function
The transcription factor contains of proteins with a secondary structure of alfa-helix.
They recognize base sequence in major groove in DNA.
, Binding transcription factor to DNA; hydrogen bonding amino acid side chain in alfa-
helix and nucleotide bases
Types of protein secondary structure;
- Helix-trun-helix; 2 alfa-helix connected by turn
- Helix-loop-helix; 2 alfa-helix connected by loop →
dimerization protein
- Zinc finger motif; 1 alfa-helix + 2 antiparallel beta-
sheets. Zn2+ hold together
- Leucine zipper motif; promotes dimerization
(vorming) of 2 transcription factor proteins, 2 alfa
helix interwind via leucine. → dimerization protein
Homodimer; two identical transcription factor proteins
together
Heterodimer; 2 different transcription factor proteins
together
Regulatory transcription factors recognize regulatory elements
Upregulation; regulation leads to increase transcription
Down regulation; regulation leads to decrease transcription
Orientation-independent/bidirectional; regulatory elements can function in forward
and reverse direction (enhancer). Dus naar onder en dan omdraaien!
The location of regulatory elements varies.
Regulatory transcription factors influence transcription
Regulation via TFIID (bind to TATA box and needed to RNA polymerase II bind to
core promotor)
Regulatory transcription factors bind to regulatory
element and then influence function of TFIID
- Activator protein → enhance ability TFIID to
initiate transcription
o Help TFIID bind to TATA box
o Facilitate ability RNA polymerase II to
bind to core promotor
→ activator proteins exert (uitoefenen) their effect
by interacting with co-activators; increase rate of
transcription, do NOT DIRECTLY bind to TFIID. →
contain transactivation domain; promotes activation
RNA polymerase by interacting with general
transcription factors
- Repressor → inhibit ability to initiate
transcription. Opposite effect as activator
Regulation via mediator (controls ability of RNA
polymerase II to progress to the elongation stage via CTD)
Mediator mediate interaction between RNA polymerase II and regulatory transcription
factors
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