Control of Gene Expression in Eukaryotes & Bacteria Flashcards
where is the main step of gene expression control?
differences in both transcription and translation
structure & function depends on transcription
Overview of gene expression
- Transcriptional control
- RNA processing control
- RNA transport and localisation control
- Translation control
- mRNA degradation control
- Protein activity control
What are the 3 different RNA polymerases?
RNA polymerase 1: mainly ribosomal genes
RNA polymerase 2: transcribes all protein coding
RNA polymerase 3: adaptors between RNA and protein
How is transcription initiated?
promoter section required for RNA polymerase to initiate transcription
transcription factor binds to control region (next to promotor)
transcription starts
What are cis-acting regulatory regions?
same molecule
DNA sequences recognised by proteins
enhancers regulatory sites distant from the promoter
promoter very close to protein coding region and TATA box
What are trans-acting proteins?
Not in the same molecule
bind to promoter and enhancer to control transcription from the gene
activators and repressors bind to enhancers
What are general transcription factors?
RNA polymerase 2 only binds to promoters with help of transcription factors
What are the steps of initiation of transcription?
- TBP subunit of TFIID binds to TATA box
- The complex recruits TFIIB to promoter
- RNA polymerase 2 & other tf recruited to promoter
4.TFIIH promotes opening of DNA & phosphorylation of RNA polymerase
What role do activator proteins play?
bind to enhancers to interact with general transcription factors
makes DNA loop around and creates the complex with the mediator
What is the modular structure of a protein?
cis-regulatory module
- where gene is transcribes & highly variable
core promoter
- if a gene can be transcribed & generally similar
coding region
- what the gene product does & highly specific
What is Gal4?
an activator protein that activates multiple galactose-inducible genes in yeast
How does chromatin structure affect function?
can provide a break on runaway basal transcription
repressors condense the chromatin
activators decondense the chromatin ready for transcription
How can chromatin be remodelled?
removal of histones
removal of histone chaperones
histone modification enzymes- changing binding affinity
What effect does the have?
makes the DNA more accessible to transcription factors
How can they be modified?
core histones can be by things covalently bonding to their N-terminal tails
or at many different sites
