Eukaryotic Translation and Processing

Question 1

What are the 3 different RNA polymerases that eukaryotic have

Answer 1

RNA poly I: makes rRNA and is insensitive to a-amanitin

RNA poly II: mRNA precursors and snRNA and strongly inhibited to a-amanitin

RNA poly III: tRNA and rRNA and is inhibited by high concentrations of a-amanitin

Question 1

In what 3 ways are eukaryotic translation more complex that prokaryotic

Answer 1

1.Eukaryotes have a nucleus so transcription and translation are not coupled.
2. Eukaryotes have chromatin-the transcription machinery must work around nucleosomes. (Chromatin
packaging represses transcription.)
3. Eukaryotes have more complex processing of mRNAs:
5’ capping, 3’ poly A tails, splicing out of intron sequences, transport out of nucleus.

Question 2

What is a-amanitin

Answer 2

-known as “the death cap.”

-a-amanitin stops RNAP II during the elongation phase of transcription. Sensitivity to a-amanitin can determine which RNA polymerase is responsible for transcribing a given RNA in vivo.

Question 3

Describe TBP of TFIID

Answer 3

TBP binds to specific sequences in eukaryotic RNA polymerase II promoters

Saddle shape

-Binds to the minor groove
of the TATA box via its concave surface
-Binding induces a large conformational change in the DNA, bending it and spreading the minor groove
-The distorted DNA may signal an active promoter, allowing RNAP II to bind

Question 4

What is the function of the chromatin remodeling complex

Answer 4

Necessary to move nucleosomes around and allow TFs, polymerases and activators access to DNA

Question 5

what type of regulation is more common in eukaryotes

Answer 5

Positive regulation- presence of chromatin means that most promoters are inaccessible to polymerases - this acts as a type of repression,

Question 6

Describe the process of chromatin remodeling complexes

Answer 6

1) Inactive conformation: Native chromatin cannot be transcribed

2) Recruitment of CRC: DNA not accessible CRC reposition nucleosomes, allowing access

3)Binding sites are exposed

4)Active conformation:
-TAP binds with its target site in DNA
-TAP recruits TFIID and TBP to the TATA box
-RNA poly holoenzyme joins the transcription complex