Term 2 Practice question: Regulatory Proteins

Question 1

Practice question

Answer 1

The binding of single regulatory proteins to 5’ upstream gene sequences called promoters determines the amount of any gene transcript present in the cell.
Using examples, discuss how this statement is true but oversimplified.
You may choose examples from eukaryotes and prokaryotes

key words
-single regulatory proteins
-promotors
- amount of any gene transcript

Question 2

In support of the statement refer to

Answer 2

• Any of the repressor proteins binding to bacterial operons
• the CAP protein causing activation
• CRO and lambda repressor in phage lambda
• Eukaryotic transcription factors binding to promoter motifs.

Question 3

Now examine the statement critically

Answer 3

Is it always single regulatory proteins?
- Some regulatory proteins bind as tetramers or dimers and not singly
-Influence of other proteins on your regulatory protein e.g. recA on lambda
- Might play a role singly but need other proteins to complete the job. e.g. (alternative)sigma factors.
-Protein complexes, mediator, splicesome

Not always just protein
- Trp co-repressor,
- allolactose inducer.
-cAMP and CAP

Does it always involve proteins binding to 5’ upstream promoters?
- Some proteins bind to other sequences. -e.g. DICER complex, anti-terminators

Question 4

Why the statement doesn’t fit every situation

Answer 4

• In prokaryotes:
• role of secondary RNA structure and terminator loops, attenuation of the Trp operon.

In eukaryotes:
- alternative splicing
-RNA stability
- chromatin remodelling