Eukaryotic Transcription

Question 1

What are the features of eukaryotic transcription not seen in prokaryotes?

Answer 1

More complex regulation
RNA Processing
Spatial and temporal separation between transcription and translation (transcription in the nucleus and translation in the cytoplasm)

Question 2

What is a Eukaryotic promoter?

Answer 2

Much like prokaryotic, DNA sequences attract the RNA polymerase to the start site.

Question 3

What is the link between the promoter and the DNA molecule they sit on?

Answer 3

The promoter always on the same DNA molecule as the gene they regulate (cis-acting elements).

Question 4

Where do the promoters for RNA polymerase II sit in regards to the start site?

Answer 4

Generally the 5’ side of the start site (with exception).

Question 5

What are the 4 promoters for RNA polymerase II?

Answer 5

1. TATA box
2. CAAT and GC box
3. Initiator element
4. Downstream core promoter element

Question 6

Where is the TATA box located and how can its promoter activity be impaired?

Answer 6

-25, mutation of a single base

Question 7

Where are the CAAT and GC box located? What strands can these promoters be found on?

Answer 7

-40 and -150 but positions of these sequences vary greatly. On template or coding strand.

Question 8

Where is the initiator element (INR) found? What is its role?

Answer 8

Centred at +1 (at the initiation site). Can compensate for an absent or degenerate TATA box and defines the start site since other promoter elements are at a variable distance from that site.

Question 9

Where is the downstream core promoter element? When will this element be present?

Answer 9

+30, commonly found in conjunction with the initiator element in genes that lack the TATA box.

Question 10

What is the difference in promoters between eukaryotic and prokaryotic transcription.

Answer 10

Eukaryotic promoter elements are recognised by proteins other than RNA polymerase itself.

Question 11

What is an enhancer sequence?

Answer 11

DNA sequences that stimulate transcription, but have no promoter activity ie cant facilitate transcription of a particular gene but can recruit factors that enhance transcription of a gene under the control of a promoter.

Question 12

In which ways can enhancer sequences have stimulatory action?

Answer 12

Can exert over a large distance of base pairs and can be upstream, downstream or in the middle of a transcribed gene.

Question 13

Which strand are enhancer sequences present on?

Answer 13

Either, template or coding.

Question 14

What are transcription factors? (TFs)

Answer 14

Proteins that bind to a promoter/enhancer elements and help recruit RNA polymerase.

Question 15

Provide an example of the process of initiation in prokaryotes.

Answer 15

Physical card 21

Question 16

What is the transcription machinery?

Answer 16

Transcription machinery encompasses the process of transcription - from the transcription complex initiating, to TFs binding, to activate or repress transcription.

Question 17

What forms the basis of functional complexity in eukaryotes?

Answer 17

Combinatorial control of transcription (combination - many controls). We need all the TFs to be present.

Question 18

What is an example of the ways hormones control gene expression?

Answer 18

Oestrogens are a steroid hormone that regulates the ovarian cycle. (Physical card 22 for how).

Question 19

Why are hormone receptors used as drug targets?

Answer 19

Use an example - Physical card 23

Question 20

What is an agonist to a receptor?

Answer 20

A chemical that binds to a receptor and illicits a biological response.