FOM 5.5.2

Question 1

Enzyme in Lysosomes? Are they stable in acidic conditions?

Answer 1

Acid hydrolases (60 diff kinds)

Yes.

Question 2

Describe endogenous substrates?

Answer 2

They come from the inside of the cell and end up in the lysosome

Question 3

Role of exonuclease in RNA turnover?

Answer 3

Cleaves at 5’ or 3’ end; 1 bp at a time

Question 4

Role of endonuclease in RNA turnover?

Answer 4

Recognizes and cleaves at a specific sequence

Question 5

Role of Exome in RNA turnover?

Answer 5

Large assembly, processes and degrades substrates. Substrate feeds thru the middle.

Proccesses: pre-rRNA and pre-tRNA into mature forms
Degrades: mRNA

Requires activating proteins

Autoantibodies in autoimmune disease

Question 6

Describe mRNA Quality Control “Stalled translation” and how it is resolved?

Answer 6

Hairpin RNA or Protein-RNA complex stalls translation resulting in half a protein and a hostage ribosome.

Resolved by “No-go RNA Decay” or NGD. Endonuclease cleaves middle then XRN1 chews from 5’ end and Exosome chews from 3’ end

Question 7

Describe mRNA Quality Control “Premature stop codon” and how it is resolved?

Answer 7

Stop codon is put in the wrong place pre-maturely resulting in a half protein. Arises from incorrect splicing.

Proofreading detects that stop codon is in the wrong place and is degraded by XRN1 and Exosome. aka nonsense mediated decay (NMD)

Question 8

Describe mRNA Quality Control “No stop codon” and how it is resolved?

Answer 8

Results from transcription aborting too early (protein too short) or adenylation too soon (protein too long)

Resolved with by nonstop decay (NSD) where exome is used to chew it up at the 3’ end

Question 9

Describe mi/siRNA binding regarding end of life mRNA turnover?

Answer 9

miRNA and siRNA are 2 groups of small regulatory RNA. When pairing occurs with the mRNA, protein complex recognizes complementarity and concentrated P bodies within the cytoplasm either stops translation from occurring or degrades mRNA