Control of Gene Expression

Controlling gene expression

Often accomplished by controlling transcription initiation.

Gene expression regulation

Controlled by regulatory proteins binding to specific DNA sequences.

Regulatory proteins

Bind to DNA to either block or stimulate transcription.

Major groove of DNA

Where regulatory proteins gain access to the bases of DNA.

DNA-binding motifs

Structures possessed by regulatory proteins to bind to DNA.

Prokaryotic organisms

Regulate gene expression in response to their environment.

Eukaryotic cells

Regulate gene expression to maintain homeostasis.

Apoptosis

A type of regulation where a cell induces programmed cell death.

Operons

Used by prokaryotes to regulate gene expression.

Cluster of genes

Under the control of a single promoter in an operon.

Transcription initiation

Can be controlled through positive or negative mechanisms.

Positive control

Increases transcription when activators bind to DNA.

Negative control

Reduces transcription when repressors bind to DNA regulatory regions.

Promoter's role

Positions and orients the RNA polymerase correctly.

Operator

The region where the repressor binds.

RNA polymerase binding region

Immediately upstream from the coding region of DNA.

Negative regulation

Uses a repressor protein to prevent transcription.

Inducible operon

An example is the lac operon, which can be activated.

Repressible operon

An example is the trp operon, which can be turned off.

trp operon

Encodes genes for the biosynthesis of tryptophan.

trp repressor protein

Negatively regulates the trp operon.

Co-repressor

Tryptophan that binds to the repressor to block transcription.

Lac operon

Contains genes to break down lactose.

CAP binding site

Part of lac operon regulatory regions.

Induction in lac operon

The process where lactose binds to the repressor and allows transcription.

Promoter of lac operon

RNA pol poorly binds to without glucose.

Catabolite activator protein (CAP)

Helps RNA pol attach and drive transcription when glucose levels are low.

Positive regulation in lac operon

Involves cAMP and CAP enhancing operon activity.

Transcription factors

Necessary to control eukaryotic gene expression.

General transcription factors

Required for proper binding of RNA polymerase to DNA.

Specific transcription factors

Increase transcription in response to specific signals.

Coactivators and mediators

Assist in the function of transcription factors.

Transcription complex

The combination of coactivators, mediators, and transcription factors.

Enhancers

DNA sequences that increase the rate of transcription.

Chromatin remodeling complexes

Modify histones, DNA, and chromatin structures for transcription regulation.

Methylation effect on gene expression

Addition of CH3 can control whether a gene is expressed.

Acetylation of histones

Makes DNA more accessible for transcription.

Posttranscriptional Regulation

Mechanisms that control gene expression after transcription.

Alternative splicing

Introns are removed from pre-mRNA to create mature mRNA.

RNA editing

Creates mRNA that is not directly encoded by the genome.

mRNA degradation

Loss of poly A tail that can affect gene expression.

Small RNAs in gene regulation

Act after transcription, influencing stability or translation.

miRNA

Micro RNA involved in gene repression.

siRNA

Small interfering RNA that can inhibit gene expression.

circRNA

Small circular RNA that can degrade miRNA and siRNA.

snRNA and snoRNA

Small nuclear and nucleolar RNA involved in RNA processing.

piRNA

Piwi-interacting RNA involved in gene regulation.

RNA interference (RNAi)

Process by which RNA molecules inhibit gene expression.

CRISPR

Clustered regularly interspaced short palindromic repeats used in genome editing.

Cas9 enzyme

CRISPR associated protein used to cut target DNA.

Ubiquitin

Protein that tags other proteins for degradation.

Proteasome

Structure where proteins tagged for degradation are broken down.

Degradation of proteins

Continually occurs in cells to regulate protein levels.

tissue-specific RNA editing

RNA editing that occurs in specific tissues, influencing gene products.

cAMP (cyclic AMP)

A signaling molecule that enhances the activity of CAP in the lac operon.

Apoptosis in regulation

A programmed cell death process influencing overall cellular health.

Operon structure

Contains multiple genes controlled by a single promoter.

Repressor vs. Activator

Repressor prevents transcription, while activator enhances it.

Regulatory regions of operons

Include promoter, operator, and binding sites for proteins.

RNA pol II

RNA polymerase involved in eukaryotic transcription.

Transcription start site

+1 position where transcription begins.

Transcription factors interactions

Coactivators and mediators bind to enhance transcription efficiency.

Gene expression variations

Can arise due to alternative splicing of a single gene.

Effect of glucose on lac operon

High levels result in low cAMP and reduced transcription.

Gene regulation in both prokaryotes and eukaryotes

Involves complex interactions between DNA, RNA, and proteins.

RNA interference outcomes

Targeted degradation of mRNA to control gene expression.

CRISPR technology impact

Revolutionized genetic engineering and research techniques.

Protein tagging for degradation

Ubiquitin attachment marks proteins for degradation.

Nucleosome remodeling mechanisms

Include repositioning of nucleosomes to allow transcription.

Histone modifications

Alter DNA accessibility and influence transcription rates.

General vs. Specific transcription factors

General factors are necessary for all genes, specific factors vary by gene.

Complexity of eukaryotic gene regulation

Involves many layers and regulatory elements.

Gene expression dynamics

Can be influenced by external signals and cellular conditions.

Chromatin structure's role in gene expression

Determines which genes are accessible for transcription.

Transcriptional activators

Proteins that bind to enhancers to increase transcription rates.

Apoptosis role in growth regulation

Ensures that damaged cells do not continue dividing.

Homeostasis in gene expression

Eukaryotic regulation aims to maintain balanced levels of gene products.

Gene promoter functions

To recruit transcription machinery and initiate transcription.

Transcription factor binding specificity

Determined by the DNA sequence and structural motifs.

mRNA stability influences

Can impact how much protein is produced from a transcript.

RNA processing importance

Critical for the maturation of functional mRNA.

RNA stability and degradation factors

Determine the longevity of mRNA in the cellular environment.

Effect of small RNAs on translation

Can prevent ribosomes from translating specific mRNAs.

Transcription complex assembly

Involves interaction of various proteins with DNA and each other.

Signal transduction and gene expression

Signals can activate or repress gene expression pathways.

Eukaryotic enhancers' unique feature

Can function at a distance from the promoter they regulate.

Positive control in gene regulation

Involves factors that enhance the likelihood of transcription.

Negative feedback in gene expression

Mechanism that prevents overexpression of genes.

Cluster of operons

Formed by related genes to coordinate their expression.

Developmental gene regulation

Involves activation and repression patterns during development.

Role of transcription factors in differentiation

Guide cell fate decisions based on gene expression patterns.

Influence of environmental factors on gene expression

External conditions can significantly alter cellular responses.

Genetic regulation by chromatin structure

Active genes tend to have more accessible chromatin configurations.

RNA processing regulation

Can be influenced by various cellular signals and conditions.

Complex layers of gene control

Eukaryotic systems utilize multiple levels of regulation for precision.

Feedback loops in gene control

Can stabilize or destabilize gene expression patterns.

Potential applications of CRISPR technology

Used for gene editing, disease modeling, and therapeutic interventions.

Methylation as a gene silencing mechanism

Inhibits transcription factors from accessing DNA.

Nuclear architecture and gene expression

Chromosome positioning can impact transcription efficiency.

Transcription factor recruitment mechanisms

Involve multiple protein-protein interactions to initiate transcription.