11.1 - Eukaryotic transcription regulation

Question 1

What are the levels of control?

Answer 1

1. Activation of gene structure: open chromatin
2. Initiation of transcription of elongation
3. RNA stability - processing the transcript
   3.a - Transport to the cytoplasm from the nucleus
4. Translation of mRNA
5. Protein modification
6. Protein transport
7. Protein degradation and transport (of mRNA)

Question 2

How is gene expression controlled principally?

Answer 2

Add one more control level
- Activation of structure; open chromatin
- Chromatin structure can persist through cell division called the epigenetic state where the properties of a gene are determined by chromatin structure

Question 3

How is the gene turned on: second mechanism?

Answer 3

• transcription factors can bind
  to DNA on outside of histones and spread: either uni or bi
  directionally until it reaches an insulator (Boundary
  element)

Question 3

How do transcriptional factors (things that turn genes on and off though DNA binding)
gain access to the promoter
region?

Answer 3

• bind to target DNA site

Question 4

How is the gene turned on: first mechanism?

Answer 4

• When replication disrupts chromatin structure, after
  the Y fork has passed, either chromatin can reform or transcription factors can bind and prevent chromatin formation

Question 5

What is an activator?

Answer 5

• Activators; determine the frequency of transcription, work by making protein–protein contacts with the basal factors, may work via coactivators, are regulated in many different ways (upregulation)

Question 6

What is an repressor?

Answer 6

• A protein that inhibits expression of a gene
• downregulation
  repression occurs when chromatin structure is affected or when it is bound or masks to activators

Question 7

What is positive regulation and provide an example?

Answer 7

• Genes cannot be expressed unless a positive regulator is bound
• In operon, activator helps RNA polymerase to open the promoter sequence that was caused by the bounding of a transcriptional factor to a promoter

Question 8

What is the first class of activators?

Answer 8

True activators
- A positive transcription factor that functions by making contact, direct or indirect, with the basal apparatus to
activate transcription through a coactivator