Regulation of Gene Expression

economical

regulation at the transcriptional level is the most

prokaryotes

Gene expression in prokaryotes or eukaryotes?

Locations of functionally related genes: often clustered in operons

eukaryotes

Gene expression in prokaryotes or eukaryotes?

Locations of functionally related genes: often distant from one another with separate promoters

prokaryotes

Gene expression in prokaryotes or eukaryotes?

RNA polymerases: one

eukaryotes

Gene expression in prokaryotes or eukaryotes?

RNA polymerases: RNA polymerase 1, 2, 3

prokaryotes

Gene expression in prokaryotes or eukaryotes?

promoters and other regulator sequences: few, simple

eukaryotes

Gene expression in prokaryotes or eukaryotes?

promoters and other regulator sequences: many, diverse

prokaryotes

Gene expression in prokaryotes or eukaryotes?

initiation of transcription: binding of RNA polymerase with associated sigma factor

eukaryotes

Gene expression in prokaryotes or eukaryotes?

initiation of transcription: binding of basal transcription apparatus, mediator, and specific transcription factors

sigma factors

direct RNA polymerases to bind specific promoters

operon

functional related genes are often clustered together and controlled by a single promoter

lac operon

genes required for metabolizing lactose

transcription regulators

recognize specific DNA sequences based on the pattern of interactions in the major and minor grooves

DNA compaction

can be used to regulate how DNA is replicated or how genes on a chromosome are expressed

by compacting the DNA around it so it is not accessible for the enzymes involves in expressing the gene

How can genes be turned off?

the structural organization of chromatin

helps regulate gene expression

chromatin

is how DNA is compacted in nondividing cells

it is condensed to further form chromosomes

in cells that are preparing to divide, what happens to chromatin

euchromatin

loosely packed chromatin is called

heterochromatin

highly condensed (tightly packaged) chromatin is called

not expressed

genes within heterochromatin are usually

Chromatin modifying enzymes

regulate gene expression by making a region of DNA either more or less accessibly to transcription machinery

eukaryote DNA

is packaged with proteins to form chromatin, which gives cells the ability to regulate transcription at the level of accessibility

histone acetyltransferases

add acetyl groups to the positive tails which neutralizes their charges, loosening the compact nucleosome and allowing regulatory proteins to bind

histone deacetylases

can remove acetyl groups from histones and thereby repress transcription

general transcription factors

bind to the core promoter, then RNA polymerase II binds and initiates transcription

blocks

binding of repressor protein _____ transcription

stimulates

binding of activator protein ______ transcription

the promoter region

regulatory protein binding sites for repressors or activators

transcription factor binding sites for general and specific factors

RNA polymerase binding site for initiating transcription

enhancer

is a DNA sequence bound by a transcription activator

enhancers

DNA binding sites that increase transcription

silencer

is a DNA sequence bound by a transcription repressor

repressors

bind to specific DNA sequences and inhibit transcription. In eukaryotes, transcription involves several steps. It occurs in both, nucleus (transcription) and cytoplasm (translation)

alternative splicing

Different mRNAs can be made from one gene by

reduce gene expression

regulatory RNAs such as microRNAS can do what to gene expression

the condensed chromatin, allowing transcription to occur

What does acetylation of histone tails open up?

negative transcription regulation

Binding of repressor protein blocks transcription, this is an example of what?

positive transcription regulation

binding of activator protein stimulates transcription, this is an example of what?

enhancers

DNA binding sites that increase transcription

mediator

binds to the basal transcription apparatus (in eukaryote gene expression)

mediators

binds specific transcription factors and the basal transcription apparatus to alter transcription rate (in eukaryote gene expression)

DNA bending

allows distantly bound transcription factors to interact with mediator (in eukaryote gene expression)

TRUE

True or False: eukaryotic gene expression can be regulated after transcription