Breaks down stuff(enzymes)

Default state is OFF (not completely)

-promoter becomes available only when the nutrient is present.

-induces enzymes 

Synthesizes something that the host cell needs all the time.

Default state is ON

It is repressed when nutrients are around.

Corepressors are essential elements like AA, nucleotides, and cofactors that attach to put together the repressor and attaches it.

Codes for repressor protein mRNA. May be seperated from Operon. Always transcribing at a low rate. Independent of cell status.

Binds and stimulates initiation of transcription by RNA polymerase. Found in Catabolic Operons ONLY. Adjacent to or overlapping promoter.

Involved with bringing lactose into the cell. Upregulates Lac Operon

Catabolic Operon

lactose→glucose

Without lactose(inducer) availability transcription is at very low levels.

When inducer is no longer present, remaining mRNA will degrade within minutes.

They bind to operator and stop translation.

Have 4 subunits (tetramer) and is a palindrom.

If it binds with regulatory gene[(I).. the gene that coded for it] it will no longer be able to bind with operator because of modifications. (I) acts as negative allosteric modifier.

Catabolic: are attached to the operator until  an Inducer or (I) attach to it and cause it to fall off.

Anabolic: essential element(corepressor) complexes with repressor to stop stop translation.

Desired product is already present so there is no need to produce anymore.

cAMP concentration decreases in the presence of Glucose. Less cAMP-CAP complexes are formed to attach to promoter.

Anabolic Operon

Always turned ON

When Tryptophan is around it acts as a corepressor and complexes with the repressor to stop transcription.

 A genetic boundary element that plays two distinct roles in gene expression, either as an enhancer-blocking element, or more rarely as a barrier against condensed chromatin proteins spreading onto active chromatin. The need for them arises where two adjacent genes on a chromosome have very different transcription patterns, and it is critical that the inducing or repressing mechanisms of one do not interfere with the neighboring gene

1. DNA is bond in Histones. Limited availability.

2. Different polymerases

3. Different initiation

4. Post transcriptional processing

5. Feedback for ribosomes. If protein is at high level translation will stop.

Cis= Intergrated with DNA 

1. Promoter sequence

2. Proximal region (Palindrome)

3. Enhancer/Silencer/Insulator(Distal region-Palindrome)

4. Response element sequence

Regardless of the presence of a promoter, there are Transcription Factor(TFs) proteins that help. Transcription factors can be modulated by proximal regions.

Proteins that interact with DNA sequences.

1. Transcription Factors: "core protein elements"

2. Gene Regulation Factors:

Proximal Promoter Element 

Enhancer/Silence/Insulator(CTCF"hundreds of them")

3. Response elements

1. Inhibition of elongation

2. Boundary Function: blocks enhancer ability to turn on transcript.

3. Silencing of initiation

They can react differently with DNA to determine if it will be a Insulator/Enhancer/Silencer.

Multivalent factor: Allows lots of variation in one molecule.

Individual contacts are weak, but all of them together are strong.

Zn can be connecting 2 pairs of Csy or a pair of Cys and a pair of His.

CAP-binding proteins(binds to cAMP)

Three a-helecies where helix 2 and 3 are in a "helix turn helix" motif.

Dimeric Structure

2 Polypeptides zip through an α-helix to form a molecule.

The Basic Regions (α-helix) interact with the DNA.

Different combinations of polypeptides can lead to a lot of variety.

2 Leucine Zippers form with a loop seperating them.

Dimeric Structure

The Basic (α-helix) Regions react with the DNA and are different depending on the polypeptides involved. Additional protein interaction happens on the opposite side of the polypeptide.

Inherited from father.

Synthesizes an antisense RNA that blocks the synthesis of mRNA for Igsr2.

An iherited difference in the expression of a gene depending on whether it is inherited from the mother or the father.

Silencer RNA

Researchers use it.

How viruses silence the host RNA.

siRNA is a double stranded RNA that is chopped up upon recognition.

Fragments bind with RISC forming a siRNA-RISC complex.

That complex binds to and cleaves the host RNA

microRNA

Involved in gene supression and many other things.

Found in the body.

NOT translated into proteins.

Coded for by part of the DNA that doesn't code for a gene.

One part of the folded RNA can bind to a specific target protein or chemical.

Another part contains the RNA code for a protein product.

Example in Euk: TPP

Example of Alternative Pormoters

Longest gene

8 promoters with each having its own initial exon.

Mutations in this gene lead to muscular distrophy.

Caused my mutation in that cause the inducer regulatory protein(CDK, Cyclin) to become hyper stimulatory.

Requires on 1 allele mutation

Functions as a tetramer(dimer of dimers)

Cause pause in G1/S phase when a problem is sensed in the DNA.

Induces p21 to block the Cyclin/CDK2 complex.

If problems can't be fixed than the cell goes on path towards apoptosis.

Disables the "emergency brake" function.

Stabilizes mutations.

Occur in over 50% of human tumors. Most frequent mutation in tumors.

-Inheritance of mutated p53 allele.

Increased chance of getting breast, brain, adrenacortical tumors, sarcomas, and leukemias.

↑Mdm2 = ↓p53

can prevent interaction of p53 with initiation complex.