Eukaryotic Gene Regulation

Question 1

Gene

Answer 1

A nucleotide sequence that encodes information for the synthesis of a functional biomolecule, for example, a protein

Question 2

Gene expression

Answer 2

Process in an organism, in which genetic information (a DNA sequence) is used to produce a functional biomolecule

Question 3

Cellular gene expression must be tightly controlled and coordinated

Answer 3

• cell growth and differentiation
• response to environmental, physiological, and developmental signals
• response to infection
• cell-to-cell communication
• maintain cellular homeostasis

Question 4

Eukaryotes

Answer 4

Three different RNA polymerases (I, II, III), composed of 14 (RNAPI), 12 (RNAPII), 17 (RNAP III) subunits.
Different RNA polymerases transcribe distinct types of RNA.

Question 5

Prokaryotes

Answer 5

Single RNA polymerase core enzyme composed of 5 subunits (α2,β,β’,ω)
Transcribes all types of RNA: ribosomal RNA
(rRNA), transfer RNA (tRNA) and messenger RNA (mRNA)

Question 6

Core promoter

Answer 6

• extends approximately 50bp upstream and downstream of the transcription start site (TSS)
• can contain specific DNA sequences – core promoter elements – that are recognised by
  components of the general transcription machinery (RNAPII +GTFs), that position and
  modulate the function of the RNAPII transcription initiation complex (TIC), and that determines the location of the transcription start site.

Question 7

Proximal promoter regions

Answer 7

• located upstream of the core promoter, generally spanning a few hundred bp to a few kbp
• contain cis-regulatory DNA sequences that are recognised by DNA-binding regulatory transcription factors, transcription activators and transcription repressors.
• regulate core promoter activity, i.e. the frequency of transcription initiation at the core promoter
• may function cooperatively with enhancers to stimulate transcription

Question 8

Distal promoter regions

Answer 8

• like proximal promoter regions, contain cis-regulatory DNA sequences that are recognised by DNA-binding regulatory transcription factors.
• unlike proximal promoter regions, are long-range control regions, typically located many kbp, often hundreds of kbp, away from the core promoter.
• unlike proximal promoter regions, can function independent of orientation to the target gene, upstream or downstream of the core promoter.
• are typically located in intergenic regions and within introns of genes; some enhancers have been found in exons.