Gene Regulation

Gene Expression

Transcription and translation of a gene to make a product.

Gene Regulation

Control of which genes are expressed, when, and how much.

Transcription Factor

Protein that binds DNA sequences and controls transcription.

General Transcription Factor

Factor needed at all promoters to assemble the transcription machinery.

Consensus Sequence

Short conserved DNA sequence recognized by regulatory proteins.

Epigenic Modification

Chemical change to DNA or histones that alters expression without changing the sequence.

Growth Factor

Signal that stimulates cell growth and division.

Operon

Cluster of genes under one promoter (prokaryotes).

Promoter

DNA sequence where RNA polymerase binds.

Operator

DNA sequence between promoter and genes where a repressor binds.

Structural Genes

Genes in an operon that code for the proteins.

Repressor

Protein that blocks transcription by binding the operator.

Inducer

Small molecule that inactivates a repressor to turn an operon on (lactose).

Co-repressor

Small molecule that activates a repressor to turn an operon off (tryptophan).

Activator

Protein that increases the rate of transcription.

Inducible Operon

Normally off, turned on by a substrate (lac).

Lac Operon

Operon for lactose metabolism in E. coli.

Trp Operon

Operon for tryptophan synthesis.

Negative Control

Regulation by a repressor.

Positive Control

Regulation by an activator.

CRP (CAP)

cAMP receptor protein; activator of the lac operon.

cAMP

Second messenger that rises when glucose is low.

Catabolite Repression

A preferred fuel (glucose) prevents use of other fuels.

Sigma Factor

Prokaryotic subunit that recognizes promoter consensus sequences.

Pribnow Box

TATAAT consensus at -10 in prokaryotic promoters.

TATA Box

Eukaryotic promoter sequence where TFIID binds.

Pre-initiation Complex

General transcription factors plus RNA polymerase at the promoter.

Enhancer

DNA sequence that binds activators and increases transcription, even from far away.

Silencer

DNA sequence that binds factors that decrease transcription.

Mediator

Protein complex linking enhancer-bound factors to RNA polymerase.

Cell Differentiation

Cells becoming specialized through different gene expression.

Post-transactional Control

Regulation after transcription (splicing, export, stability).

Alternative Splicing

Joining exons in different ways to make different mRNAs.

RNA Stability (half-life)

How long an mRNA lasts before it is degraded.

UTR

Untranslated region of mRNA that affects stability and translation.

RNA-binding Protein

Protein that binds mRNA to control stability or translation.

siRNA and miRNA

Small RNAs that bind mRNA and block translation or cause degradation.

RNA Interference (RNA silencing)

Gene silencing by small RNAs.

Translational Repressor

Protein that blocks translation of an mRNA.

Histone

Protein that DNA wraps around.

Nucleosome

DNA wound around a core of histones.

Chromatin Remodeling

Changing nucleosome structure to open or close DNA.

DNA Methylation

Addition of a methyl group to cytosine; represses transcription.

CpG Island

CG-rich region, often in promoters, where methylation occurs.

Histone Acetylation

Addition of acetyl groups to histone tails; activates transcription.

Histone Acetyltransferase

Enzyme that adds acetyl groups to histones.

Histone Deacetylase

Enzyme that removes acetyl groups; represses transcription.

Epigenetics

Study of heritable changes in expression not caused by DNA sequence changes.