Topic 11 Eukaryotic Gene Regulation Flashcards
How is transcription is eukaryotes diff from in prokaryotes
Eukaryote:
More genes spaced further apart (more noncoding genes)
Have 3 rna polymerases (prokaryotes have 1)
Pol1: rRNA
Pol2 mRNA
Pol3 tRNA
Transcription happens in nucleus
DNA is packaged into chromatin
How is transcription initiated in eukaryotes
General transcription factors bind to sequences in the promoter
Then RNA pol 2 gets positioned at +1 site
This all makes the PIC (preinitiation complex where the c-terminal domain (CTD) of rna pol 2 is phosphoylated by TFllH
This phosphorylation makes a binding site for enzymes to make the 5’ M7G cap in the premrna
What is the m7G cap
A methylate guanine nucleotide that’s added to the 5’ end on the mRNA
Protects mRNA from decay from exonucleases
Helps in splicing and translation
What is the polyA tail
Sequences in The 3’ UTR of mRNA signal for rna pol to be cleaved off, and then for the poly A tail to be added the 3’ mRNA end
Addition of 50-250 adenosines the protects mRNA from decay and helps in translation
What does splicing of introns do
The 5’ GU and 3’ AG in the intron are recognized by spliceosome
Diff cuting of introns make mutiple diff mature mRNAs which can make many diff protiens
In mature mRNA what is in each region:
M7g cap
5’ UTR
Start codon
Coding region
Stop codon
3’UTR
POLy a signal
Poly a tail
Protections from exonucleases, help recruit ribosomes
Landing site for ribosomes (Kozack sequence)
First translated codon methionine
Translated to amino acid sequence
Terminated translation
Protection/regulatory functions
Processing sequence for poly a tail
Protects and exports mRNA
What are transcription factors
What are regulators
Directly bind to dna
Don’t directly bind to dna
What are coacticators and coreoressors
Corefulators that activate transcription
Corefulators that repress transcription
Transcription factors can be both activators and repressor
What is the core promoter
What is the enhancer
The region surrounding the transcription start site, where the general transcription factors bind
Thousands of base pairs upstream or downstream of transcription start site. It loops to get closer to the promoter to enhance/turn on transcription
What do coregulators do in terms of the enhancer and promoter
They bring the enhancer closer to the promoter to help promotes transcription
What can tfllD act as
Both transcription factor and coactivator
What are the 4 domains of transcription factors , which are required, what do each do
DNA binding domain: required
Dimerization domain: optional, homo (same 2 proteins interacting) hetero (diff 2 proteins) dimers
Ligand binding domain: optional, hormone or vitamin, allosteric site changes conformation of the transcription factor
Activation/repression domain: required
What enzymes are involved in import and metabolism of glucose in the GAL system
What chromsome is each on
GAL1, GAL7, GAL10 : chromsome 2
Gal2: chromosome 12
What are the regulatory protiens in the gal system
GAL4 GAL3 GAL80
Regulate transcription of the enzyme encoding genes
What happens in the gal system when there’s is no galactose?
Enzyme encoding genes are not expressed because nothing to break down and import
What happens in the gal system when there’s is galactose?
Enzyme encoding genes are expressed because stuff to break down and import is here
What is gal 4 and what does it do
It’s a transcription factor (binds to dna)
binds to the upstream activation sequence (UAS) of GAL7,10,1,2 in the dna to activate transcription.
Made up of activation domain, dimerization domain, DNA binding domain
Always expressed
What are gal 3 and gal 80
Gal 80 is a repressor of gal 4 (stops activation of transcription)
Gal 3 in the presence of galactose undergoes a conformational change then Binds to gal80 to stop it from inhibiting gal 4 (transcription can start)
Gal 3 and gal 80 are always on
What are histone octamers
Have 8 total proteins, two each of H2A, H2B, H3, and H4
Positively charged
Have a folded core and tails that intact with adjacent nucleosomes and other proteins
What is heterochromatin
More compact
Constitutive heterochromatin: dna that’s always compact, regions aren’t transcribed
Facultative heterochromatin: either compact or non compact
What is euchromatin
Less compact
Transcriptionally active (is being transcribed)
What is included in chromatin modification
Histone modification
DNA modification
How are histones modified and what is histone acetylation
Modified in the histone tails, adding an acetyl group to a lysine amino acid on the tail
What are the two affects of acetylation
Reducing chromatin compaction by loosening the interaction between histone and dna
Creates a binding site for the bromodomain which is found in transcriptional activatiors (turns on genes)
Bromodomain binds to acetyl group on the histone tail
Is a bromodomain a dna binding domain
No, coregulator
What is HAT
HDAC
HMT
HDM
histone acetyl transferase (adds acetyl to tail
histone deacetylase (removes acetyl)
Histone methyl transferase (adds methyl
Histone demethylase (removes methyl)
What is the histone code hypothesis
Different combos of histone modifications specify different transcription outcome
Do promoter and enhancers get transcribed
No
What is DNMT
DNA methyltransfease
It recognizes a CpG (CG) site in dna and adds methyl to it
What are CpG islands? When are they methylate and unmethylated
Where are they found
CpG islands are clusters of unmethylated CpGs
They are unmethylated in expressed genes (actively transcribed)
Methylated in unexpressed genes
They are found in promoter, intragenic (in gene) and intergenic (out gene)
Unmethylated CpG island are…..
Methylated are ….
Euchromatin and active transcription
Closed chromatin and repressed transcription
What type of inheritance are dna methylation and histone modifications accosiated with
Epigenetic (on top of, influenced phenotype not dna sequence)
What does parent of origin maternally imprinted mean
Means the copy of the gene derived from the mother is silenced, not expressed, it is methylated
This is an epigenetic mechanism where and identical gene is inactive or active depending on if it was derived from mother or father
