week 3 - transcriptional regulation - eukaryotes

Question 1

why is eukaryotic gene transcription regulated

Answer 1

• differential gene expression regulated by the combination of different transcription factors in that cell determine cell differentiation and identify/ function
• gene expression is regulated in response to extra - or intracellular signals to mount the appropriate cellular response

Question 2

how is gene expression regulated

Answer 2

• primary control point: initiation of transcription
• cells have distinct sets of transcription regulators, some work to increase transcription, others prevent or suppress it, such that only a fraction of the genes in a cell are expressed at any one time

Question 3

how is gene expression increased or decreased in response to environmental change

Answer 3

in prokaryotes : nutrient availability

in eukaryotes : a large number of regulatory proteins in combination

Question 4

what are potential points for the regulation of gene expression

Answer 4

1. remodelling of chromatin : results in increased promoter accessibility for transcription to initiate
2. transcriptional regulation (pre-mRNA synthesis)
3. pre-mRNA splicing (transcript processing)
4. transport to the mRNA (from nucleus to cytoplasm)
5. mRNA stability
6. translational control at the ribosome (protein synthesis)
7. post - translational modification of proteins (ie phosphorylation)
8. protein degradation (proteasome)

Question 5

regulation of transcription in eukaryotes

Answer 5

• general transcription factors binding the core DNA promoter to recruit RNA polymerase; required at every gene
• transcriptional activator or repressor proteins bind to DNA regulatory elements to influence transcription levels

Question 6

what are transcriptional activators

Answer 6

DNA-binding activity and transcription activation are carried by independent domains of an activator

transcriptional activators are modular

Question 7

what is the role of the DNA-binding domain

Answer 7

to bring the transcription - activation domain into the vicinity of the promoter

Question 8

homo- and heterodimers can recognise different DNA sequences

Answer 8

-2 different monomers give 3 possible dimers

-different combinations will recognise different sequences

-they may also exert differences effect on transcription