Lecture 8: Eukaryotic Gene Expression 2

Question 1

What is a nucleosome?

Answer 1

“Fundamental subunit of chromatin”
~200bp wound in two turns around an octamer of histones

There is very little difference between the histone proteins of different organisms (humans vs tomato’s e.g.,) - VERY IMPORTANT

Question 2

What is euchromatin? What is heterochromatin?

Answer 2

Euch: Open & expressed chromatin

Hetero: closed and not expressed

Question 3

What are the two classes of nucleosome remodelling?

Answer 3

1. ATP-dependent nucleosome
   modellers
   a. e.g., SNF
2. Modifiers of histone acetylation

Question 4

What are the ATP-dependent nucleosome remodeller families

Answer 4

1. SWI2/SNF2 family
2. ISWI family
3. Mi-2 family

Question 5

What do ATP-dependent nucleosome remodellers do?

Answer 5

1. “Remodelling” - remodelling of protein bound to upstream activator sequence - loosened
2. “sliding” - move nucleosome away from upstream activator sequence
3. “Transfer” - transfer nucleosome to different region of DNA - ‘Acceptor DNA’

Question 6

What do ATP-dependent nucleosome remodellers do?

Answer 6

1. “Remodelling” - remodelling of protein bound to upstream activator sequence - loosened
2. “sliding” - move nucleosome away from upstream activator sequence
3. “Transfer” - transfer nucleosome to different region of DNA - ‘Acceptor DNA’

Question 7

How does histone acetylation work?

Answer 7

End terminal histone tails are rich in
positively charged amino acids (e.g., Lys,
Arg) = BIND TIGHTLY TO NEGATIVE DNA

1. Lysine's reversibly acetylated by histone 
   acetyl transferases (HAT)
2. Acetylation = less positive charge
3. DNA binding is less tight
4. Histone deacetylases (HDAC) - remove 
    acetyl group

Question 8

What is factor acetylation (FAT)

Answer 8

Acetylation of a none histone group