Lecture 4: Eukaryotic Gene Regulation Flashcards
(31 cards)
What types of RNA are found in both eukaryotes and prokaryotes
mRNA
rRNA
tRNA
What are the different types of RNA polymerase found in eukaryotes and prokaryotes?
prokaryotes only have one type of RNA polymerase
eukaryotes:
RNA polymerase I: rRNA
RNA polymerase II: protien-coding genes
RNA polymerase III: tRNA
TFIID
recognises TATA box
What five general transcription factors are required for eukaryotic transcription
H, B, D, F, E
What is a mechanism that gene regulatory proteins can act over very large distances
DNA loping
Describe coactivators and corepressors
assemble on DNA-bound gene regulatory proteins. DO NOT directly bind DNA
DBD
DNA Binding Domain
recognizes specific DNA sequence
AD
Activation domain accelerates frequency/rate of transcription
What transcription factor is needed in prokaryotes
Sigma factor; initiates transcription
What is a mediator in eukaryotic transcription
acts as an intermediate between regulatory protiens and RNA polymerase
How do binding locations of coactivators and corepressors vs transcription factors differ
coactivators and corepressors assemble on DNA-bound gene regulatory proteins and do NOT directly bind to DNA
Transcription factors bind to cis regulatory elements ON DNA
decribe the modular design of eukaryotic activator protiens
two parts; can mix and match (evolutionarly and with biotechnology)
1) DNA binding domain (DBD) recognizes a specific DNA sequence
2) Activation domain (AD acceperates frequency/rate of transcription
Overall, how do activator protiens activate transcription?
Attract, position, and modify:
- General transcription factors
- mediators
- RNA polymerase
They do this by:
- acting directly on these components (binding to transcriptional machinery)
or
- acting indirectly by modifying chromatin structure to increase promoter accessibility (TATA)
Describe nucleosomes
the base structure of eukaryotic chromatin including around 200 nucleotide pairs od DNA wrapped about 2 2/3 times around a histone octamer (consisting of H2A, H2B, H3, and H4 2 times)
Two models of how nucleosomes pack
zigzag model
solenoid model
What are the four major ways activator proteins can alter chromatin
1) Nucleosome sliding allows access of transcription machinery to DNA
2) Transcription machinery assembles on nucleosome-free DNA after histone removal
3) histone replacements allow greater access to nucleosomal DNA
4) Specific patterns of histone modification destabalize compact forms of chromatin and attract components of transcriptional machinery
Describe nucleosome sliding
nucleosome structure is altered by chromatin-remodelling complexes in an ATP-dependant manner to increase promoter accessibility
How is histone removal and exchange preformed
requires cooperation with histone chaperones
ATP dependant
Exchange is btwn H2A-H2B dimers
Removal occurs by exchanging the nucleosome core (histone octamer)
What is the signal for chromatin remodelling
presence of the chromatin remodelling complex
Where and how do histone modifications occur
occur on specific amino acids of histone tails by histone-modifying enzymes called “writers”
Where is it most common to have histone modifications
N-terminus tail sticking out of the histone, though can also occur on the C-terminus
Describe Human Interferon regulation, stepwise
1) activator protein binds to DNA and attracts HAT
2) HAT acetylates H3K9 and H4K8
3) activator protein attracts HK
4) HK phosphorylates H3S10
5) HAT acetylates H3K14
6) TFIID and chromatin remodelling complex bind to modifies histone tails and initiate transcription
What is HAT and what does it do
histone acetyltransferase acetylates H3K9, H4K8, and H3K14
What is HK and what does it do
Histone kinase phosphorylates H3S10
