T3 modules 3: eukaryotic transcriptional regulation

Question 1

what is responsible for cellular differentiation

Answer 1

gene regulation
- stem cell differences in embryonic development (regulated by transcription factors)

Question 2

Genetic organization in eukaryotes (structure and function)

Answer 2

unlike prokaryotes, genes controlled by their own promoters and enhancers

HISTONE
- nucleosme
- histone proteins (8 in a nucleosome)
- histone tails (positive charge)

HISTONE REMODELLING
before: DNA wrapped
- positive charged histone tails interact with negative charge DNA (tight wrap)
after: DNA unwrapped
- tails acetylated
- activator pr- recruits enzyme histone acytyl transferase (HAT)
- charge lessened, DNA loose so transcriptional
- tails can also be methylated and phosphorylated, changing the charges on the tails

Question 3

transcription-acting factors

Answer 3

regulate eukaryotic transcription
-able to bind once DNA has been unwound
4 types
- basic helix-loop-helix
- helix-turn-helix
- zinc finger
- leucine zipper
HB bond occur between AA on helix and functional groups on DNA

once bound to DNA, assumes confirmation that starts transcription

Question 4

sequences required to start transcription

Answer 4

within CORE PROMOTER
- (-25) TATA box recognized by TFIID transcription factor
- (-35) BRE region bound by TFIIB transcription factor

ENHANCER REGIONS (upstream of core promoter)
- transcriptional activator proteins bind here

DNA loops to connect transcriptional activator proteins to RNAP. The mediator complex connects them.

Question 5

transcriptional regulation

Answer 5

silencer regions
- upstream of gene being transcribed
- when repressor protein binds, translational processes disrupted (e.g. mediator activity and general transcription factor assembly)

Question 6

blood cell progienitor differentiation in adults vs babies

Answer 6

stem cells
- differentiate into red blood cells
- activates transcription of GLOBIN PROTEINS (make up hemoglobin)
- everyone has 2 alpha-globin
-BABIES have 2 gamma, ADULTS have 2 beta
- gamma globin binds O2 better than beta

difference in transcription - DNA open or closed depending on what type of globin protein needed

Question 7

modification after transcription factors have binded

Answer 7

DNA METHYLATION
- CpG islands
- when C not methylated: DNA binding pr- can recognize promoter and bind
- when C methylated: binding site shape changes, binding pr- can’t bind
- methylation state heritable from cell to cell

some pr- can only bind to methylated DNA - HISTONE DE-ACYTYLASE (HDAC)
- this pr- promotes de-actylation of histone tails so DNA wraps back up and transcription is further inhibited