TMC 7 - Gene regulation

Question 1

most common mechanisms by which transcription can be turned up or down in prokarytes and eukaryotes

Answer 1

prokary + eukary:
- Presence or absence of a repressor
- presence or absence of an activator
in eukarys only – they are also regulated by their chromatin state:
– if chromatin is in its 30nm format - inaccessible to RNA transcription - gene is turned off - cant be regulated
– if chromatin is in 10nm format - gene is accessible – can be up regulated

In mammals – transcription can also be regulated by the methylation state:
– under methylated promoters - active
– over methylated promoters - silent

Question 2

CpG methylation of DNA only occurs in mammals – transcription can also by regulated by the methylation state in mammals

Answer 2

yes

Question 3

What protein can be used as a biomarker for myocardial infarction (heart attack)? explain why this
protein can be used vs. a protein like GAPDH.

Answer 3

cardiac-specific troponin I (TNNl3)
This is a tissue specific protein and can thus act as a biomarker whereas GAPDH is a houskeeping protein ie. the gene for this protein is expressed in all cells and thus is not specific to the heart. thus cant be used as a biomarker.

Cardiac-specific troponin I (TNNl3) is abundant protein only
produced in the heart tissue - when the heart is damaged eg. in a heart attack
- heart cells lyse and release some of their contents into the blood - the amount of cardiac-specific troponin I in the blood reflects the amount of cardiac muscle damage that has occurred- this is a valuable test for assessing
whether chest pain is due to a heart attack.

Question 4

What is the difference between a strong promoter and a weak promoter with respect to gene expression?

Answer 4

• promoters vary depending on how well they promote transcription
  – range from strong to very weak
  – strong promoters - high amts of RNA produced from genes w/ strong promoters
  – weak promoters - low amts of RNA produced from genes w/ weak promoters

Question 5

What are the main similarities and differences between transcription regulation in prokaryotes, eukaryotes and mammals?

Question 6

Give an example of a housekeeping gene and a tissue specific gene.

Answer 6

Housekeeping genes/proteins:
- about 5-10% of genes are expressed in all cells and these genes encode the “housekeeping proteins.”
- These carry out essential activities to keep the cell alive like - transcription, translation and energy production
- Examples:
—— RPS13 which encodes ribosomal protein 13
—— GAPDH which encodes an enzyme in glycolysis
- the genes encoding these proteins are expressed in all cells.

Tissue specific genes:
Different tissues have different patterns of protein expression related to the function of the tissue.
EXAMPLES:
— Beta cells in pancrease - and no others - produce insulin
—- Beta globin produced in RBCs
—- RYR1 receptor produced in skeletal musc. cells
—- large amts of cardiac-specific troponin I (TNNl3) produced in cardiac cells

Question 7

Outline the key concepts in transcription regulation.

Question 8

what is a gene promoter

Answer 8

A site in a DNA molecule at which RNA polymerase and transcription factors bind to initiate transcription of specific genes to mRNA.