Module 4 Section 7 Flashcards

1
Q

Post transcriptional gene silencing (PTGS)

A
  • silenced genes are still transcribed, but the resultant mRNAs are degraded before they can be translated into proteins
  • was first identified as co-suppression
  • increased gene lead to increased mRNA lead to decreased protein
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Micro RNA expression and processing

A
  1. miRNAs first transcribed as primary miRNA (pri-miRNA) with one or more sets of internally complementary sequences that can fold to form hairpin-like structures
  2. pri-miRNAs cleaved by nuclear endonucelase (Drosha) to produce shortened hairpins (60-70 nucleotides)
    - have a 5’ phosphate and 2-nucleotide 3’ overhang
    - now called precursor miRNAs (pre-miRNA)
  3. pre-miRNAs bind to export receptor proteins, transported from nucleus to cytoplasm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

siRNA and miRNA gene silencing

A
  1. Once in cytoplasm, pre-miRNAs cleaved by Dicer ribonuclease to produce 20-22 nucleotide ds-miRNA
    - miRNAs incorporated into RNA-induced silencing complex (RISC), includes AGO protein
  2. After cleavage, miRNA is unwound, the unneeded passenger strand is discarded
  3. the strand complementary to the target is delivered to a particular mRNA by AGO protein
  4. once mRNA has been targeted, degree of miRNA-mRNA base pairing leads to either AGO-mediated degradation (high complementarity) or translational repression (lower complementarity), followed by degradation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

miRNA binding

A
  • generally bind to 3’ UTR of an mRNA in animals
  • can make reporter plasmid with coding for 3’UTR of interest downstream of a gene that codes for a fluorescent protein (luciferase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Regulation of gene expression by Non-coding RNAs

A
  • long non-coding (lncRNA) and circular (circRNA) RNAs have multiple functions, one is to compete as targets for miRNA binding
  • contain miRNA binding regions, miRNA response elements (MREs)
  • when miRNAs bind non-coding RNAs instead of target mRNA, results in increased translation of the gene of interest
  • known as ‘competing endogenous model’
How well did you know this?
1
Not at all
2
3
4
5
Perfectly