Gene Expression Gene Expression Transcription Splicing Polyadenylation mRNA Stability Translation Protein Stability Controls on Protein Levels Transcription Control Prokaryotic Promoter Transcription Control Prokaryotic Promoter ID: 811095
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Slide1
Gene Expression
Dr. Kevin Ahern
Slide2Gene Expression
Slide3Gene Expression
Transcription
Splicing
Polyadenylation
mRNA Stability
Translation
Protein Stability
Controls on Protein Levels
Slide4Transcription Control - Prokaryotic Promoter
Slide5Transcription Control - Prokaryotic Promoter
Polycistronic Message in Prokaryotes
Slide6Transcription Control - Prokaryotic Promoter
Allo-Lactose
Lactose
Slide7Transcription Control - Prokaryotic Promoter
Slide8Transcription Control - Prokaryotic Promoter
Slide9Transcription Control - Prokaryotic Promoter
CAP
CAP Site of DNA
cAMP
Slide10From Wikimedia Commons
Transcription Control - Prokaryotic Promoter
Slide11From Wikimedia Commons
Prokaryotic Transcription Control - Termination/Attenuation
Slide12Prokaryotic Transcription Control - Termination/Attenuation
Slide13Transcription/Translation Control - Riboswitches
Anti-terminator
Terminator
Cis-acting sequences
Slide14Transcription/Translation Control - Riboswitches
Lysine Bound to Riboswitch
Slide15Eukaryotic Gene Expression
Much More Complexity
Chromatin
Many Transcription Factors
Enhancers
Slide16Transcriptional Control - Eukaryotes
Slide17Increasing Magnification
RNA
Eukaryotic Gene Expression - Chromatin
Chromatin is the Complex of DNA, Protein, and RNA Comprising Eukaryotic Chromosomes
For RNA Polymerase to Perform Transcription, Access Must Be Gained to the DNA
Slide18RNA
Eukaryotic Gene Expression - Epigenetics
Slide19RNA
Eukaryotic Gene Expression - Chromatin
A Nucleosome is a Fundamental Unit of Chromatin Structure
Contains Two Copies Each of Four Histone Proteins - H2a, H2B, H3, and H4
DNA is Wrapped Around this Octet Core and Histone H1 is on the Outside
Slide20RNA
Eukaryotic Gene Expression - Chromatin
Histone Proteins Are Rich in Basic Amino Acids, Making Them Positively Charged
The Positively Charged Proteins Are Attracted Strongly
to the Negatively Charged Phosphates of the DNA
Chemical Modifications That Affect These Charges Influence Transcription
Slide21RNA
Eukaryotic Gene Expression - Chromatin
Slide22RNA
Eukaryotic Gene Expression - Chromatin
Histone Acetyl Transferases (HATs) Use Acetyl-CoA to Put Acetyl Groups on Lysines in Histones
This Neutralizes Their Positive Charge and Loosens Interactions With the Histones, Facilitating “Remodeling” or Restructuring of Chromatin to Allow Transcription to Occur
Acetylated Lysines Can Also be Binding Targets for Proteins Affecting Transcription
Chemical Modification
Unwinding of Complex
Slide23RNA
Eukaryotic Gene Expression - Epigenetics
Slide24RNA
Eukaryotic Gene Expression - Chromatin
Histone Acetylation Favors Euchromatin and Stimulates Transcription
Histone De-Acetylases Reverse These Effects, Favoring Heterochromatin and Gene Silencing
The Sirtuin 1 deacetylase in humans down-regulated with insulin resistance
Numerous Chemical Modifications are Made to Histone Proteins
Acetylation / Deacetylation
Methylation / Demethylation
Phosphorylation / Dephosphorylation
Ubiquitination
Chemical Modification to Bases in DNA
Can Also Affect Transcription
Open and Accessible to
Transcription Complex
Condensed and
Not Accessible
Slide25RNA
Eukaryotic Gene Expression - Epigenetics
Slide26Epigenetics
Chemical Modifications in Histones and DNA Can Cross Generational Barriers
Transcriptional Effects Can Thus Be Transmitted From Parent to Progeny
Independent of the Sequence of the DNA.
Such Influences are Called Epigenetic
Slide27Slide28Transcriptional Control - Eukaryotes
Methylation of CpG sequences in
eukaryotes inhibits transcription
Slide29Transcriptional Control - Eukaryotes
Slide30Slide31Transcriptional Control - Eukaryotes
Slide32RNA
Eukaryotic Gene Expression - Transcription
Insulators Can Block Enhancer’s Activation of Transcription
Blocking Insulators Allows Enhancer to Activate Transcription
Slide33Iron Transfer & Storage
Ferritin - Cellular Protein to Bind Iron
Transferrin Receptor - Membrane Protein to Transfer Iron
Slide34Iron Transfer & Storage
Iron Response Element (IRE)
Iron Response Element
Binding Protein (IRE-BP)
Slide35Iron Transfer & Storage - Translation Regulation
Slide36Iron Transfer & Storage - mRNA Stability
Slide37RNA
RNA Interference
RNA Interference is a Powerful Means of Controlling Gene Expression
Viral and Endogenous Cellular Genes Are Targets
A Similar System Called piRNA (piwi RNA) Protects Against Transposon
Genes
Considerable Interest in Using Technique to Genetically Transform
Organisms for Protect Against Pathogens
Slide38RNA
RNA Interference
Cellular Source
Cellular Pre-Processing
Double-Stranded RNA is Stimulus
Target Complementary Sequences in mRNAs
Viral Infection
Transcription
Processing
RISC
RISC
20 bp pieces
Slide39RNA
RNA Interference
RISC
+
mRNA
Complementary Sequences Align
RISC
Argonaute Activity
in RISC Breaks
mRNA, Stops
Translation
RISC
+
Translation of mRNA Stopped
Slide40RNA
RNA Interference
Protection Against Invading Viruses
Stimulated by dsRNA
miRNA (cellular) & siRNA (foreign)
Cellular piwi RNAs (piRNA) have similar functions in silencing transposons
Widespread in Eukaryotes
Actions referred to as RNA Interference (RNAi)
RNA Interference Operates Through the Silencing of Gene Expression
DS RNA induces Dicer to chop it into 20 BP Pieces
These siRNAs/miRNAs bind to the RNA Induced Silencing Complex (RISC)
One Strand is Destroyed and One Retained to Bind to Complementary
mRNA sequences
RISC Nuclease Activity (Argonaute)
1. Destroys mRNA Where Strand Binds or
2. siRNA/miRNA strand on mRNA blocks translation or
3. si/RNA/miRNA strand destabilizes mRNA and Targets for Destruction
Slide41RNA
RNA Interference
Bonding to mRNA
Premature
Stopping of
Translation
Degradation of
mRNA