RNA Flashcards
In what ways is RNA different from DNA?
RNA is shorter
RNA is single stranded (vs ds DNA)
RNA can form secondary loop and stem structures (e.g. tRNA)
What is the most abundant form of RNA in the cell
rRNA
RNA is synthesized ___’ to ___’
5’ to 3’
Does RNA require a primer?
No
What is the function of the beta subunit of RNA polymerase?
Contains the catalytic site
What is the function of the sigma subunit of RNA polymerase?
Recognizes the promoter region of RNA
Does transcription transcribe the whole genome?
No, there are discreet areas that are transcribed.
How do promoters work in eukaryotes?
2 sequence elements at -35 and -10
What piece of RNA polymerase recognizes and binds to the promoter region?
Sigma subunit
What are the steps of transcription?
- Initiation
- Elongation
- Termination
What is the committed step of transcription initiation.
Moving from a closed promoter to an open complex with 2 open strands. Transcription bubble always 12 bases wide.
RNA almost always starts with a ____.
Purine
How long is the RNA-DNA hybrid in the beta subunit of RNA Polymerase?
8 bases
What sequence signifies transcription rho-independent termination site?
GC-rich palindrome followed by UUU
(a self-complementary sequence!)
UUU forms a hairpin loop
A small fraction of transcription termination is __________.
Rho-dependent
How does rifampicin work?
It inhibits the formation of the first phosphodiester bond in transcription initiation
How is eukaryotic transcription different than prokaryotic?
- Three polymerases
- No sigma subunit
- Polymerase-protein interactions govern specificity
What does RNA Polymerase I do?
Large rRNAs (28s, 18s, 5.8S) in the nucleolus
What does RNA Polymerase III do?
Transcribes the precursors of small RNAs (tRNAs and 5S rRNAs)
What does RNA Polymerase II do?
Transcribes the precursors of mRNAs
Does RNA Polymerase II have a sigma factor?
No! Instead Pol II interacts with specific PROTEINS which bind core promoter regulatory elements
What are key features of the eukaryotic promoter?
Further from beginning of transcription than prokaryotes
TATA box/basal element (-25)
Additional constitutive elements -40 to -110
Inducible elements -150
What do constitutive elements in the eukaryotic promoter do?
Govern the RATE of transcription
What do inducible elements do?
Cause initiation of transcription in response to hormones or very specific environmental stimuli
What binding factors must proceed binding of Pol II?
TATA binding protein (TBP), TAF, TFIIA-F
What is TFIIH?
A binding factor that phosphorylates Pol II to initiate transcription
What type of protein binds to enhancers.
Activators
What are the components of the core promoter?
Basal element
Constitutive element
Inducible element
How does chromosome remodeling and histone acetylation/deacetylation affect transcription?
Affect efficiency of transcription initiation
Are constitutive elements always on to some degree?
Yes
How are death cap mushrooms toxic?
Alpha-amanitin inhibits RNA Pol II in eukaryotes.
