Control of Gene Expression in Eukaryotes

Question 1

What are transcription factors?

Answer 1

Transcription factors a group of proteins responsible for finding specific genes within a DNA strand to initiate transcription. Each transcription factor is a large protein made up of of smaller parts (domains) for special jobs.

• Typically before gene regulation takes place

Question 2

What are the two important domains on transcription factors and what special function do they serve?

Answer 2

1. The first transcription factor domain is the DNA binding domain which binds to specific nucleotide sequences.
2. The second transcription factor domain is the activation domain which recruits and binds several transcription factors and regulatory proteins.

Question 3

What are response elements?

Answer 3

Response elements are sequences of DNA that binds specific transcription factors for the gene need to make more products (protein).

• It works from the same promoter region that initially regulates transcription.
• Extra transcription factors come and find your response elements to fulfill extra demand.

Question 4

What are cis and trans regulators?

Answer 4

1. Cis regulators are regulators located in close proximity to the gene on its DNA strand and are actually part of the DNA (not protein or RNA).
   
   • Response elements, promotor regions, and enhancers are all examples of cis regulators
2. Trans Regulators are regulators that travel from far distances in different parts of the cell and is not part of the DNA.
   
   • Transcription factors are an example

Question 5

What is the first line of attack to produce more gene products if needed, but what is the second if even more product is needed?

Answer 5

The first initial response to needing an upregulation of a gene is a response element. However, if more even product is required, an enhancer region is utilized.

Question 6

What is an enhancer?

Answer 6

An enhancer is a region that assists in amplifying gene expression and is made up of multiple response elements.

• Enhancers are actually just a bunch of nearby response elements that work together to produce maximum product (protein).

Question 7

What do histone acetylases do?

Answer 7

Histone acetylases add acetyl groups to histones which weaken the interaction between histones and DNA. This converts heterochromatin into the loose, open conformation (euchromatin) activing genes to be transcribed.

• Histone acetylation increases gene expression.
• Histone deacetylases remove acetyl groups from histone converting euchromatin back into heterochromatin.
  
  • Histone Deacetylation decreases gene expression.

Question 8

What does DNA methylases and DNA demethylases do?

Answer 8

DNA methylases add methyl groups to nucleotides on DNA which prevents transcription.

• Transcriptional complex machinery (RNA polymerase) is unable to bind to DNA when DNA is methylated.
• DNA methylation decreases gene expression.

DNA demethylases remove methyl groups from nucleotides and allows transcription to occur.

• Unblocks transcriptional machinery
• DNA demethylation increases gene expression

Question 9

Summarize which mechanisms increase and decrease gene expression within eukaryotic cells.

Answer 9