Gene Regulation: The control of protein production Prokaryotes Eukaryotes A. Small circular genome B.Unicellular (DNA instructions for only one cell type) C. Most DNA codes for protein D. Most of the genome is expressed E. Mechanism: The OperonThe Operon I. Differences between gene regulation of prokaryotes and eukaryotes A. Large genome, many strands, genes randomly distributed among the strands B. Multicellular (DNA instructions for every cell type of the organism) C. Most DNA as “junk DNA” (Repetitive DNA that make introns, centromeres, telomeres)junk DNAcentromeres, telomeres D. Little of the genome is expressed (20% max) E. Mechanisms: 1. Chromosome Structure 2. Transcriptional Control 3. Post-Transcriptional Control 4. Translational Control 5. Post-Translational ControlPost-Translational Control Chapter 18 pages

II. The Operon System Parts of the Operon A. Structural Genes: The sequence of genes required to produce the desired product. Many are part of the same metabolic pathway and are in a specific order.specific order B. Promoter: Area of the DNA that allow attachment to the of RNA polymerase D. Regulatory gene: Produces a protein that interacts with the operator C. Operator: Part of the DNA that when bound to a specific protein will prevent the attachment of RNA polymerase E. Types 1) Inducible operons example: Lac operonexample: Lac operon 2) Repressible operons example: Tryp operonexample: Tryp operon

The Lac Operon: Controls the production of enzymes required to metabolize lactose Lac operon turned off Promoter Regulatory gene mRNA Repressor Protein (active) RNA polymerase Structural genes Operator 1. Active repressor binds to the operator Lac operon turned on Lactose Inactive repressor RNA polymerase mRNA Operator Regulatory gene Repressor Protein Lac ZLac YLac A Galactosidase Permease Transacetylase 1. Lactose binds to active repressor and deactivates the repressor 2. RNA polymerase bonds to promoter allowing the transcription of the structural genes Slide 2Why is it called an “inducible operon”? 2. RNA polymerase can not transcribe structural genes (no lactose present) (lactose present) Video Promoter Structural genes

The Tryp Operon: Controls the enzymes required to build tryptophan (amino acid) Operon turned offOperon turned on Regulator gene Operator Structural genes mRNA Tryptophan Inactive repressor Active Repressor 1. Inactive repressor is made active in the presence of tryptophan Active Repressor RNA Polymerase Inactive repressor Enzymes required for the synthesis Tryptophan synthesis Tryp ATryp BTryp CTryp DTryp E 1. Inactive repressor can not bond to the operator Slide 2 Regulator gene Operator 2. Tryptophan is not synthesized since RNA polymerase cannot bond to promoter 2. RNA polymerase bonds to DNA so the enzymes for the synthesis of tryptophan are transcribed Why is this called a “repressible operon”? (Tryptophan present)(Tryptophan absent) Promoter

Areas of Control in Eukaryotic Cells Control TypeFunction / ExamplesMethods Chromosome Structure Structure 1. Histone Acetylation 2.DNA MethylationDNA Methylation 1. Spreads out nucleosomes to facilitate transcription 2. Makes genes inaccessible (Barr Bodies and Imprinting) Transcriptional Control 1.Transcription factors bond at promoter site to increase RNA polymerase affinity 2.Activator proteins bind to DNA Enhancers to bend DNA to form transcription initiation complex 1. Hormones & Signal TransductionHormones & Signal Transduction 2.Formation of transcription complexFormation of transcription complex Albumin (liver) vs. Crystalin (lens) Post Transcriptional Control Translational Control Post Translational Control 1. mRNA processing introns and exons 2. mRNA export 3. Long lived or short lived mRNA 1. Intron and exon splicing will modify the protein producedIntron and exon splicing will modify the protein produced 2. 5’ Cap and Poly A tail can prevent export to cytoplasm 3. RBC have long lived mRNA 1.Translation Repressor Protein binds to 5’ Cap preventing translation 2.Non-Coding RNAs a. MicroRNA (miRNA)MicroRNA (miRNA) b. Small Interfering RNA (siRNA) 1.mRNA prevented from translation in egg until after fertilization 2.Non-coding RNA that binds with protein that degrades or prevents the translation of coding RNA 1. Protein Processing modifies the activity of proteins 2. Selective degradation 1. Insulin and Digestive Enzymes 2. Targeting by a) ubiquitinubiquitin b) ProteasomesProteasomes

SteroidSteroid Hormone Gene ActivationProtein Hormone Gene Activation Hormones and Transcription Factors Slide 5

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Levels of DNA Packaging Slide 5

How Introns and Exons Control Gene Expression

Proteasomes in the cytosol Protein Modification: Proteasomes Slide 5

Organization of Prokaryote Genes Slide 3 Slide 4

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Slide 1

Androgens are illegal because they work!! Slide 6

How Activators and Enhancers Influence Transcription Slide 5 (Proteins made by cell) (DNA Codes)

How 2 Different Cells with Identical DNA can Produce Different Proteins (Blood Protein) (Eye Lens Protein ) Slide 5

The Effect of Histone Acetylation

Origin and Function of MiRNA Coded mRNA Slide 5