Week 9 - Gene Regulation

7 Control Points - Where

Chromatin

Transcription

mRNA processing

mRNA transport

RNA stability/degradation

Translation

Post translational modification

6 Mechanisms - How

DNA binding proteins

Riboswitches

Two component systems

Hormones

Epigenetics

Non coding RNA

Structural Genes

Functional proteins

Regulatory Genes

Control other genes

Constitutive Genes

Housekeeping

Constantly expressed

Inducible Genes

Normally off

Repressible

Normally on

Positive Control

Inducer must bind

Negative Control

Corepressor must bind

DNA Binding Proteins - Bind via

H bonds with bases

Interactions with backbone

Helix Turn Helix

1 helix in major groove

1 helix stabilise

Zinc Finger

Loop of amino acids held by Zn ion

Leucine Zipper

Leucine residue helix + basic helix

Parallel dimer via hydrophobic interactions

2 adjacent major grooves

DNA Binding Proteins - Types

Trans factors

Nucleases

Polymerases

Histones

Replication - helicases + topoisomerases

Repair

Riboswitches

Regulatory segment of mRNA that directly binds to target molecule

Riboswitches - Transcriptional Control

Target molecule binds

Conformational change - hairpin

RNA pol fall off

Premature termination

Riboswitches - Translational Control

Target molecule binds

Conformational change - RBS not accessible

Ribosome cant bind

No translation

Two Component Systems

Detect external signal & respond

Two Component Systems - 2

Transmembrane Sensor

Intracellular Response Regulator

Transmembrane Sensor Protein - AKA

Histidine kinase

Transmembrane Sensor Protein

Detect external stimulus

Autophosphorylation - PO4 from ATP to own histidine

Intracellular Response Regulator Protein

PO4 transferred to aspartate residue

Act as transcription factor

cis acting

Within same DNA strand

trans acting

Proteins that act on any DNA strand