Eukaryotic Regulation Of Gene Expression

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4 Levels of Control

Back 1

1. Transcriptional

2. Posttranscriptional

3. Translational

4. Post translational

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histones

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Type of protein that structurally organizes eukaryotic chromosomes. It compacts the length of DNA so that it can fit into the nucleus

( Transcriptional , 1. organization of chromatin)

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nucleosome

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DNA wraps around 8 histones to form this structure. A length of DNA wound twice around a spool of histone proteins.

( Transcriptional , 1. organization of chromatin)

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solenoid

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binding of histones causes nucleosomes to package into a coiled structure called this

( Transcriptional , 1. organization of chromatin)

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linker DNA

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connects adjacent nucleosomes (beside each other)

( Transcriptional , 1. organization of chromatin)

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euchromatin

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loosely packed region, genes active in RNA transcription, light stain

( Transcriptional , 1. organization of chromatin)

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heterochromatin

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densely packed region, inactive in RNA transcription, dark stain

( Transcriptional , 1. organization of chromatin)

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Chromatin remodelling complex

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pushes aside histones so that a promotor is accessible and transcription can begin

( Transcriptional , 1. organization of chromatin)

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Barr Bodies

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evidence that heterochromatin is inactive in females, on x chromosome

example - female calico cat

( Transcriptional , 1. organization of chromatin)

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x- inactivation

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in mammalian female, when chromosomes condense and have a dark stained mass

- spots on female calico cat

( Transcriptional , 1. organization of chromatin)

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transcription factors

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how fast a gene is transcribed depends on which one of these is bound to the DNA

(Transcriptional, 2. regulatory proteins)

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RNA polymerase

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activates transcription - binds to promotor region adjacent to the gene to be transcribed, unzips, links RNA nucleotides

(Transcriptional, 2. regulatory proteins)

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Transcription factor

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bind to the promotor

(Transcriptional, 2. regulatory proteins)

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Transcription activators

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binds to enhancer

(Transcriptional, 2. regulatory proteins)

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hairpin loop

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shape of DNA molecule for transcription to begin

(Transcriptional, 2. regulatory proteins)

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polytene chromosomes

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consists of hundreds - thousands of copies of the same DNA molecule

(Transcriptional, 3. number of copies of genes)

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drosophila polytene chromosome

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giant polytene chromosomes form in their salivary glandes by repeated DNA replication

(Transcriptional, 3. number of copies of genes)

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Alternative splicing

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process in which axons are removed or joined in various combinations

(Posttranscriptional, 1. mRNA processing)

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intron

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non coding region, "in-between"

(Posttranscriptional, 1. mRNA processing)

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exon

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coding region, "expressed"

(Posttranscriptional, 1. mRNA processing)

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sex determination in drosophila

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determines whether it turns male/female by alternative splicing, a cascade of ran splicing reactions

(Posttranscriptional, 1. mRNA processing)

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nuclear pore complex (NPC)

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controls the entry/exit of molecules in and out of the nucleus

(Posttranscriptional, 2. mRNA transport)

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inportins

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karyopherin, to enter the nucleus

(Posttranscriptional, 2. mRNA transport)

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exportins

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karyopherin, to exit the nucleus

(Posttranscriptional, 2. mRNA transport)

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Ran

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regulates inportins and exportins in/out of the cell

(Posttranscriptional, 2. mRNA transport)

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RNA-binding proteins

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mRNA are packaged in large particles that are formed as RNA binding proteins that coat the mRNA. Example : yeast, under stress

(Posttranscriptional, 2. mRNA transport)

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masked messengers

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faster way to undergo translation. example: clams and frogs; mRNA molecules are unmasked as soon as fertilization takes place, then a burst of translation producing proteins needed for development

(Translational, 1. masked messengers)

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initiation factors

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bind to leaders, allow subunits of ribosomes to assemble around mRNA, proteins or other molecules can bind and can restrict or enhance initiation

(Translational, 2.initiation factor)

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inhibitor protein

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translation is decelerated/prevented when this binds to the leader

(Translational, 2. initiation factor)

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enhancer protein

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translation is accelerated when this binds to the leader

(Translational, 2. initiation factor)

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ribonuclease

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enzyme that destroys mRNA

(Translational, 3. life expectancy of mRNA)

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Hormone stabilization of mRNA

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hormones can prolong the life expectancy of mRNA. example is prolactin

(Translational, 3. life expectancy of mRNA)

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proinsulin -> insulin

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proinsulin is inactive, a sequence of about 30 amino acids is enzymatically removes from the middle of the molecule and results in an active insulin

(Posttranslational, 1. additional chemical modifications)

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digestive enzymes

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increase activity by pro-enzyme activation

(Posttranslational, 1. additional chemical modifications)

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feedback control

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controls activity of a protein, during a biochemical reaction, the end product binds at an allosteric site on an upstream enzyme and activates or inhibits it

(Posttranslational, 2. feedback control)

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allosteric activation

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Control of enzyme activity by a regulatory molecule or ion that binds to a region outside the enzyme’s active site.

(Posttranslational, 2. feedback control)

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proteasomes

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breaks down damaged proteins, with hydrolysis

(Posttranslational, 3. longevity of proteins)

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Alzheimers disease

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linked to malfunction of proteasomes

(Posttranslational, 3. longevity of proteins)