Regulation of Transcription Flashcards
What is the difference between anti-termination mechanisms of N and Q of lambda phage?
N acts at the ends of immediate early genes whereas Q acts on immediate late genes
What is the function of cII gene in lambda phage?
cII promotes transcription from a leftward promoter (Panti-Q) within Q, promoting Q antisense RNA which blocks the production of Q. Q is required for late transcription in the lytic phase, so interfering with its synthesis favors lysogeny
What is the function of cIII gene in lambda phage?
cIII protects cII from destruction by proteases in the cell. They work together to establish lysogeny by activating PRE and PI
Explain the possible outcomes in the race between cro and cl
If cro wins, lytic cycle results
If cl wins, lysogeny results
Which environmental conditions promote lysis and which conditions promote lysogeny?
Lysis requires more energy than lysogeny. So when glucose is abundant, lysis occurs
What specific genes are transcribed by each of the 3 RNA polymerases?
I: pre-rRNA for 18, 5.8, and 28s rRNA
II: pre-mRNA, some snRNA
III: pre-tRNA, 5S rRNA, and some snRNA
What is the function of the zipper within the clamp?
Initiates the dissociation of template DNA
What is the function of the rudder within the clamp?
Initiates the dissociation of the RNA-DNA hybrid
What is the function of the lid within the clamp?
Maintains dissociation
How does the bridge helix mediate transcription within RNA polymerase II?
The bridge helix positions the template strand for decoding, oscillating between straight and bent conformations. When straight, the active site is open for nucleotide addition by polymerase, filling in the space between the 3’ end of RNA and straight bridge helix. During translocation, the bridge helix shifts to the bent space. When it straightens again, it reopens the active site at the 3’ end of RNA
What is the order in which the general transcription factors are added to the preinitiation complex?
- ) TFIID
- ) TFIIA
- ) TFIIB
- ) TFIIF
- ) TFIIE
- ) TFIIH
What is the function of TFIID?
Contains TATA-box-binding protein (TPB) and 8-10 TBP-associated factors. Interaction with promoter is the first step in formation of the pre-initiation complex.
What is the function of TFIIA?
Stabilizes binding between TFIID and promoter to form the DA complex
What is the function of TFIIB?
Positions polymerase at transcription start site, stabilizes TBP-TATA binding and interacts with transcription activators that bind to upstream elements.
What is the function of TFIIF?
Binds polymerase and brings it to the DAB complex. Made up of 2 polypeptides: RAP30 and RAP70. Reduces nonspecific interactions between polymerase and the DNA.
What is the function of TFIIE?
Increases TFIIH affinity
What is the function of TFIIH?
Phosphorylates RNA polymerase II
What are the 2 enzymatic activities of TAFII250?
- ) Histone acetyltransferase (HAT) attaches acetyl groups to lysines on histones, usually activating transcription by opening up DNA
- ) Protein kinase can phosphorylate itself, TFIIF, and to a lesser extent TFIIA and TFIIE
How does phosphorylation modify activity of the pre-initiation complex?
Phosphorylation modifies efficiency of assembly of the pre-initiation complex
What is the function of TBP?
Functions with RNA pol II promoters with a TATA box as well as RNA pol I, II, and III promoters without a TATA box. It is a universal transcription factor needed for transcription in eukaryotic cells
What is the main role of TFIIF?
The main role of TFIIF is to bind the polymerase and direct it to promoters containing the DAB complex
How is TFIIF similar to the prokaryotic sigma factor?
It reduces non-specific interactions between polymerases and DNA
Which enzymatic form of TFIIH carries out RNA chain elongation?
IIo, the phosphorylated form
Which general transcription factors are required for promoter clearance but not elongation?
TFIIE and TFIIH
