Regulation of Gene Expression (molecular biology)

MicroRNAs

(mRNAs) originate from DNA that is formed scattered across the genome

Short interfering RNAs

(siRNAs) are generated from dsRNA that originated outside the cell

What does the operon include?

-promoter -operator -structural genes -regulatory gene

What are two ways cell differentiate?

1. Cytoplasmic determinants 2. Cell-cell signals

Why is the regulation of gene expression in eukaryotic cells more complicated than in prokaryotes?

1. Multicellularity 2. Chromosome complexity 3. Uncoupling of transcription and translation

What are two types of proteins produced by regulatory genes?

1. Repressor protein 2. Activator protein

Transcription complex

A group of various proteins that are associated with RNA pol activity. Components of the complex include: 1. General transcription factors 2. Specific transcription factors 3. Coactivators and mediators

Corepressor

A molecule that binds to a repressor to activate it

Operator

A region engaged by a regulatory protein to either block or promote the action of the RNA polymerase

Inducible operons

A substance is required to induce (turn on) the operon

Operon

A unit of DNA that contains multiple genes whose products work together to direct a single metabolic pathway

Coactivators and mediators

Additional proteins that contribute to the binding of transcription complex components.

Protein degradation

As proteins age, they lose their functionality as their 3D shape changes.

RNA processing

Can produce different mRNAs by slicing the primary RNA transcript in different ways.

Histone modification

Changes in organization of histone proteins with DNA. Two types that can increase access to DNA transcription are acetylation and methylation.

X inactivation

Chromosome inactivation in females

Structural genes

Contain coding DNA - DNA that codes for various related enzymes that direct the production of some particular product

Determination

The series of events that lead to observable differentiation of a cell

RNA interference (RNAi)

Gene silencing caused by short RNA molecules that bing to complementary sequences of mRNAs in the cytoplasm and block their translation or cause their degradation (by cleavages). Two types are microRNAs and short interfering RNAs.

Homeotic genes

Genes that control pattern formation

What is an example of positive regulation?

Glucose repression because an activator protein is involved. When glucose is absent in the environment, CAP protein is activated and binds to operator, promoting RNA transcription of enzymes to occur.

What are two types of operons?

Inducible and repressible operons

Cytoplasmic determinants

Maternal substances in the egg that influence the course of early development. These are distributed unevenly in the early cells of the embryo and result in different effects.

DNA methylation

Methyl groups (-CH3) attach to DNA bases. This makes it more difficult for transcription factors to access the DNA.

Methylation

Methyl groups can be attached to histones. This can either increase or decrease transcription of genes. This is associated with repressed transcription.

Cell-cell signals

Molecules (like growth factors) produced by one cell influence neighbor cells, which causes cells to differentiate.

Regulatory genes

Produces the regulatory protein that engages the operator region and governs whether RNA pol can attach to the promoter region and being transcription. The protein becomes active or inactive only when they bind o some specific molecules.

Activator protein

Promotes the attachment of RNA pol to the promotor region. These proteins characterize positive regulation because they must be active in order for the transcription to occur.

Specific transcription factors

Proteins associated with regulating SPECIFIC transcription activities. Two types are activators and repressors.

General transcription factors

Proteins that are required by all transcription events to successfully initiate transcription by RNA polymerase

Promoter

Sequence of DNA to which the RNA polymerase attaches to begin transcription

Pattern formation

Sets up the body plan and is a result of cytoplasmic determinants and inductive signals. This determines the head, tail, and body orientation.

Repressible operons

Stop producing enzymes only in the presence of a repressor

Acetylation

The attachment of an acetyl group makes the histone molecules loosen their grip on the DNA molecule. This is associated with activated transcription.

Stem cells

These are cells in the early stages or embryonic development. When stem cells divide, the daughter cells have the potential to become any kind of cell.

Induction

The process by which molecules cause a cell response and causes cells to differentiate

What do specific transcription factors do?

They attach to enhancers (DNA binding sites), which can be thousands of nucleotides upstream/downstream from the gene. Because they can be so far away, the DNA segment containing the enhancer folds such that it can join the general transcription factors and RNA pol on the promoter

What do general transcription factors do?

They attach with the RNA pol to the promoter region upstream and adjacent to the gene to be transcribed

Lac operon

This controls the breakdown of lactose in E coli. A regulatory gene produces an active repressor that binds to the operator region --> RNA pol unable to transcribe genes. When lactose is available, some combines to inactivate repressor --> RNA pol able to transcribe genes that code for the enzymes the break down lactose. This is an example of negative regulation.

Transcription initiation

This is regulated by a transcription complex, and the makeup of the complex determines the degree to which transcription is activated or repressed.

mRNA degradation

This occurs as a result of RNAi, and because mRNAs are unstable molecules. Degradation of the poly A tail occurs as mRNA ages.

trp operon

This operon produces enzymes for the synthesis of the amino acid tryptophan. This is an example of negative regulation 1. A regulatory gene produces an inactive repressor that does not bind to the operator --> RNA pol transcribes genes and produces trp 2. Trp in environment --> E coli don't need to make it themselves 3. Induces some remade trp to react with the repressor to make it active (acts as a corepressor) 5. The active repressor binds to the operator region --> prevents transcription of genes

Repressor protein

This protein blocks the attachment of RNA pol to the promoter region. These characterize negative regulation because they must be inactive in order for transcription to occur.