Eukaryotic Gene Regulation I Flashcards
steps at which gene expression can be regulated
- transcriptional control
- RNA processing control
- RNA transport and localization
- translational control
- mRNA degradation control
- protein activity control
transcriptional control
which genes, when and how often a gene is transcribed
RNA processing control
control the splicing and processing of RNA transcripts
RNA transport and localization
control which mRNAs are transported out of the nucleus and where they go in the cytoplasm
translational control
select which mRNAs are translated
mRNA degradation control
selectively destabilize certain mRNAs in cytoplasm
protein activity control
selectively activate, deactivate, or locate specific protein molecules after they have been made
Why are transcriptional controls paramount?
limits the energetic and materials cost of aborting expression at any subsequent stages; fast and cheap
gene organization in prokaryotes
operons, poly-cistronic DNA for genes encoding proteins that function together, and no introns
gene organization in eukaryotes
no operons, monocistronic, each gene has separate promoter, introns
prokaryotic transcription
no histone proteins (no chromatin) so RNA polymerase always has some access to DNA, can have attenuation since transcription and translation are coupled, RNA pol only needs one general TF
similarities in eukaryotic and prokaryotic transcriptional mechanisms
requirement for cis acting sequences, requirement for gene regulatory proteins (TFs), weak and reversible protein-protein interactions, DNA looping
cis-acting DNA elements
promoter, enhancers, silencers
regulatory sequences (enhancers/silencers) can be located _
upstream, downstream, or within gene
promoter
where RNA polymerase and other TFs bind to initiate transcription, located upstream of transcription start site
enhancers are bound by _
activators
silencers are bound by _
repressors
enhancers induce _
euchromatin formation
trans-acting proteins in eukaryotes
general TFs, site-specific regulatory proteins, remodeling machinery, and mediator
general transcription factors
RNA pol II requires 5 general TFs
site-specific regulatory proteins
recognize special DNA sequences and bind to DNA –> recruit factors to regulate rate of transcription (co-activators or co-repressors)
common structure of site-specific gene regulatory proteins
DNA binding domain and effector domain(s)
Foxa1 transcription activation
Foxa1 can bind closed chromatin because it resembles H1 –> will replace H1 and induce formation of euchromatin –> once bound, will recruit chromatin remodeling machinery and histone modification enzymes –> DNA now accessible to additional regulatory proteins (ex. androgen receptor)
activators recruit _
histone modification enzymes, chromatin remodeling proteins, co-activators, general TFs, RNA polymerase II
