Day 15, Lecture 4 (Sept 13): Molecular and Cellular Networks Flashcards Preview

MCS > Day 15, Lecture 4 (Sept 13): Molecular and Cellular Networks > Flashcards

Flashcards in Day 15, Lecture 4 (Sept 13): Molecular and Cellular Networks Deck (22):
1

Most Cellular functions are regulated via 

2

All the places in Red are spots that if a mutation is to occur you could get cancer

3

4

Nonsense mediated decay (NMD)

5

____ nonsense mutation result in effective nonsense mediated decay (NMD) while _____ mutations lead to ineffective NMD

  • Primal nonsense mutations result in effective NMD while distal nonsense mutations (e.g. in the last exons) lead to ineffective NMD

6

Proximal nonsense mutations often result in ____ while distal mutation result in 

  • Proximal nonsense mutations lead to loss of function due to nonsense mediated decay
  • While Distal mutations result in truncated proteins
    • Dominant negative effects

7

What happens if a nonsense mutation is just proximal  to an EJC

The signal does not work very well and the protein will most likely still be secreted even though it is truncated

8

Iron transporter is regulated by 

  • levels of iron
    • RNA-binding protein regulates Fe transport during Fe deficiency

9

  • Iron is stored by ___, which is required at ___ Fe levels .

10

_______ absorb Fe and is required at ____ Fe levels 

11

Expain how Transferrin receptor and Ferritin are regulated

  • Iron Response element (hairpin)- binding protein IRE-BP is activated by decreased levels of Fe 
  • IRE-BP binds to the Iron Response Hairpin located on the mRNA for both ferritin and transferrin receptors (TfR) 
  • The difference in action is based on the location of the binding
    • In ferritin mRNA IRE-BP binds to the 5' UTR thus blocking the ribosome and inhibiting translation initiation
    • In transferrin mRNA IRE-BP binds to the 3'UTR thus protecting mRNA from degradation 

12

microRNA (miRNA) regulation of gene expression

  • Short RNA molecules can degrade transcripts (post-transciptional gene regulation) or induce heterochromatin (transcriptional gene regulation)

13

miRNA Post-Transcriptional regulation of gene expression 

  • Pre-miRNA is clipped into shorter sections by dicer to form miRNA
  • This and Ago+ other RISC proteins combine to make single stranded miRNA
    • this then acts on the its subsequent RNA sequence to lead to degradation 

14

What is the difference between siRNA and miRNA

  • miRNA (endogenous)
  • siRNA (exogenous) 

15

miRNA Transcriptional regulation (heterochromatin formation)

  • Pre-miRNA is clipped into shorter segments by dicer to form miRNA
  • miRNA combines with Ago and other RITS proteins (note that this is RITS and not RISK, which is the Post-transcriptional protein)
  • goes into the nucleus and clips onto DNA segement
  • recruits HMT and DNMT and leads to histone methylation and DNA methylation (thus forms heterochromatin)  to inhibit transcription 

16

DNA double-strand breaks can induce _______ arrest and apoptosis 

G1/S

17

18

Explain the mechanism/pathway for double stranded breaks cell cycle inhibition

  • A double strand break leads to the phosphorylation of ATM dimer (inactive)
    • this leads to a phosphorylated ATM monomer (active) 
  • Once activated ATM does 2 things:
    • It recruits proteins to fix the double stranded break (MRE11, RAD50, Nibrin) and BRCA1
    • Phosphorylates check 2 
  • Check2 phosphorylated (active) is now able to phosphorylate p53 thus making it stable and active 
  • p53 leads to cell cycle arrest at G1/S and apoptosis 

19

20

21

22

Decks in MCS Class (40):