L19 Eukaryotic Post-transcriptional regulation

Question 1

Post-transcriptional control

Answer 1

• mRNA stability
• mRNA translatability
• mRNA localisation

Question 2

RNA localisation

Answer 2

see onenote

• targeting RNA

After under going one division, can switch to another mating type
Unless cells have become a mother, they are not capable of switching mating types

Question 3

Homothallic and heterothallic strains

Answer 3

homothallic (HO) - strain can mate with themselves

heterothallic (ho) - strain must mate with opposite mating type

HO dominant over ho

Question 4

Cell Fate Determination - Swi5

Answer 4

see onenote

HO expression controlled by Swi5 and Ash1

WT swi5 => HO in mother and no HO in daughter

swi5 deletion => no HO in either mother or daughter

SWI5 overexpression => HO in both mother and daughter

Question 5

Looking at swi5 expression

Answer 5

see onenote

Daughter has swi5 but cannot switch mating type, not swi5 driving process for cell fate determination as it is in both of those cells

Question 6

Cell fate determination - Ash1

Answer 6

See onenote

WT Ash1 => HO in mother but not in daughter

Ash1 deletion => HO in both

Ash1 overexpression => in neither

opposite phenotype to swi5

Question 7

Looking at expression of Ash1

Answer 7

see onenote

Ash1 localised in the daughter
Only in daughter cell, not present to great extent in mother
Protein not asymetrically distributed but the RNA, when RNA for ash1 produced they are transported to the daughter cell and not the mother cell

Question 8

Ash1 movement

Answer 8

see onenote

Question 9

Post-transcriptional control

Answer 9

see onenote

RNA processing

Question 10

Regulation of mRNA processing

Answer 10

see onenote

Splicing

Question 11

Dosage compensation

Answer 11

Mammals
- random X inactivation in females

Drosophila
- upregulation of exp. for genes on X chromosome (as if there were two chromosomes)

Question 12

Regulation of mRNA processing - Dosage compensation

Answer 12

see onenote

Splicing control in sex determination

• ratio of X to autosomes important
• Regulation of mRNA processing - Dosage compensation

Sxl

• sex lethal gene
• female pathway => sxl gene on
• male pathway => sxl off

Question 13

Splicing control in sex determination - regulated splicing

Answer 13

see onenote slides

Sxl

Tra = transformer gene
Transforms male into female

Dsx = double sex gene

Question 14

Transcriptional control

Answer 14

• DNA modification
• chromatin
• transcription initiation

Question 15

Transcriptional control - Nuclear structure

Answer 15

• nucleus not homogenous

- position of genes can affect expression: nuclear scaffold, chromosome territories e.g. active, inactive

Question 16

Transcriptional control - chromosome structure

Answer 16

see onenote

• position of genes on chromosome can affect expression
• heterochromatin
• euchromatin
• position effect variegation

white gene near heterochromatin barrier => variegated gene expression

Question 17

DNA methylation

Answer 17

see onenote slides

• Occurs at CpG doublets
• two classes of DNA methylases
  1. de novo methylase
  2. maintenance methylase e.g. after dna replication

Question 18

DNA methylation - silencing of gene expression

Answer 18

see onenote

methylation + proteins that bind methylated DNA

+ histone deacetylase
+ chromatin-remodelling complex
=> gene completely off

Question 19

DNA methylation - histone

Answer 19

see onenote

• can affect recruitment of histone modifying enzymes

Question 20

Chromatin

Answer 20

see onenote

Nucleosomes

Core histones:
H1, H2A, H2B, H3 and H4

Histone variants:
H2A.X, H2A.Z, CENPA, H5

H5 functions as a linker, specific to a nucleosome
Histone variants change properties of nucleosome

Question 21

Histone variants

Answer 21

see onenote