Summary of chapter 15: Gene regulation in eukaryotes 1: transcriptional and translational regulation. Pay attention: there are figures and tables mentioned from the Genetics analysis & principles seventh edition. These are not put directly into the summary, so it is convenient to have the book read...
Chapter 15: Gene regulation in eukaryotes I: transcriptional and translational regulation
Eukaryotes = protists, fungi, plants and animals.
Gene regulation can occur at any step in the pathway of gene expression
15.1
Transcription factor = a category of proteins that influence the ability of RNA polymerase to
transcribe DNA into RNA.
General transcription factor = required for the binding of RNA polymerase to the core promoter and
for progression to the elongation stage. Necessary for any transcription to occur.
Regulatory transcription factor = regulate the rate of transcription of target genes. They influence the
ability of RNA polymerase to begin transcription of a particular gene.
Up regulation = An activator binds to an enhancer sequence on the DNA to increase the rate of
transcription.
Down regulation = A repressor binds to a silencer sequence on the DNA to decrease the rate of
transcription.
Combinatorial control = the combination of many factors determines the expression of any given
gene. There are several examples:
- One or more activator proteins stimulate the ability of RNA polymerase to initiate
transcription.
- One or more repressor proteins inhibit the ability of RNA polymerase to initiate transcription.
- The function of activators and repressors are modulated by binding of small effector
molecules, protein-protein interactions and covalent modifications.
- Regulatory proteins may alter the composition or arrangement of nucleosomes in the vicinity
of a promoter, hereby affecting transcription.
- DNA methylation may inhibit transcription, either by preventing the binding of an activator
protein or by recruiting proteins that change the structure of chromatin in a way that inhibits
transcription.
- The formation of heterochromatin may inhibit gene expression in localized regions of a
chromosome.
Domain = a specific function of an enzyme.
Motif = structurally similar regions.
- helix = has a proper width to bind to the major grooves of the DNA double helix.
In the major groove, the DNA is in contact with the cellular fluid. Hydrogen bonding between amino
acids in the - helix and the nucleotide bases are how the transcription factor binds to a DNA
sequence. Another way is that the positively charged amino acids bind to the negatively charged
backbone of DNA.
See figure 15.3 for the structural motifs found in transcription factor proteins.
Dimerization = an addition reaction.
Homodimer = two identical transcription factors being added up together.
Heterodimer = two different transcription factors being added up together.
Orientation – independent / bidirectional = a regulatory element can function in the forward or
reverse direction. If you flip the sequence and the enzyme, it will be the exact same construction.
Regulatory elements can be at a distance of 100 000 bp from the core promoter and still have an
impact.
Transcriptional regulation via TFIID:
TFIID is a general transcription factor that binds to the TATA box and recruits RNA polymerase ll to
the core promoter.
See figure 15.4 for effects of regulatory transcription factors of TFIID.
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