Transcription Regulation Review Notes

The review session is driven by student questions.
Public questions benefit the entire class, as others may share the same uncertainties.
The final exam will only cover material from the previous week.
Today's lecture content is more advanced and won't be on the exam, but it's valuable for tying concepts together.
Key topics for the exam:
- Components of a gene.
- Identifying a gene.
- Promoter function.
- Mechanism of transcription (promoter, transcription factors, RNA polymerase).

Transcription regulation is a fundamental mechanism for biological diversity.
The basic approach involves introducing a concept, outlining basic rules, and then examining regulatory mechanisms.
Regulation adds layers of complexity, enabling 'go/no-go' decisions and information processing.

mRNA analysis from different cell lines (prostate, lung, brain, kidneys, ovaries) reveals gene expression patterns.
mRNA is purified and analyzed to determine which parts of the genome are transcribed in specific cells.
Green indicates above-average gene expression; red indicates below-average expression.
Gene expression varies significantly between cell types.
Proteins are separated by weight and isoelectric point using two-dimensional gel electrophoresis.
Isoelectric point: The pH at which a molecule carries no net electrical charge.
Amino acids have different charges depending on pH and their nature.
Proteins migrate based on their isoelectric point in an electric field.
Each dot on the gel represents a protein within a cell.

Regulation can be binary (expressed or not) or quantitative (different expression levels).

The promoter and toning sequence are key components.
The promoter includes elements like the TATA box.
Transcription factor binding to the promoter can either enhance or inhibit RNA polymerase recruitment.

Enhancers and silencers are upstream regulatory sequences that influence transcription.
Enhancers promote RNA polymerase recruitment.
Silencers inhibit transcription.
The presence of specific transcription factors is cell-type dependent.

Enhancers can be located far from the minimal gene unit.
DNA looping brings enhancers into proximity with the promoter.
Transcription factors bind to upstream regulatory sequences.
The effect depends on whether the bound proteins enhance or inhibit RNA polymerase recruitment.

Neurons responding to different neurotransmitters (e.g., glutamate, dopamine) can have similar setups with slight variations.
Neurons in different circuits (e.g., memory, learning) may require different levels of sensitivity.
Example: Rat maze experiment with cheese and electric shock: the brain strengthens the circuit to remember this.
Differential transcription of dopamine receptors affects neuronal responses.
Titrating factors allows for functional differences between similar cell types.

Liver cells can be converted into neurons by forcing the expression of three neuron-specific transcription factors.
This leads to morphological and functional changes characteristic of neurons.
Transcription factors are master regulators of cell identity.
Changing a few key proteins (transcription factors) can alter the expression of hundreds of other proteins.

Transcription can be regulated in response to changing physiological conditions.
Examples: weight gain, hypertension, drug use.
Signal transduction pathways regulate transcription.
Transcription factors can be post-translationally modified (e.g., phosphorylated).
Phosphorylation can control DNA binding.
During development, cell fate decisions rely on signal transduction pathways.