RNA Editing. Definition : any process, other than splicing, that results in a change in the sequence of a RNA transcript such that it differs from the sequence of the DNA template Discovered in trypanosome mitochondria Also common in plant mitochondria
Definition: any process, other than splicing, that results in a change in the sequence of a RNA transcript such that it differs from the sequence of the DNA template
Investigators generated cDNA clones to some of the kinetoplast mRNAs and sequenced them
Sequences were partially complementary to pseudogenes on maxicircle DNA
the COXII DNA sequence above is missing 4 Us found in the mRNA
Called this “Editing” because it produced functional mRNAs and proteins from pseudogenes
Cytochrome oxidase III
From Trypanosoma brucei
Lower case Us were inserted by editing.
The deleted Ts (found in the DNA) are indicated in upper case.
Editing is from 3’ to 5’ along an unedited RNA.
TUTase, or terminal uridylyl transferase, adds U(s) to the 3’ end created by cleavage of the pre-mRNA
from Fig. 16.20
Determined by comparing sequences of cDNA copies of mt RNAs with the corresponding genomic gene.
Possible mechanism for plant Mt editing: Deamination of cytosine (to uracil) by a cytidine deaminase
- both forms circulate in blood but have different functions
- the long form is endocytosed via the LDL receptor; the short form is not
(Splicing precedes editing)
Produced by Unedited mRNA
Produced by Edited mRNA
– apobec (apoB mRNA editing enzyme catalytic subunit)
Inosine also acts as a signaling molecule.
ADA deficiency is a metabolic disease.
1st case: Glutamate Receptor B
I read as G during translation, R instead of Q
Affects Ca2+ permeability, intracellular trafficking of receptor
<- key for editing of GlutR
Other possible functions:
- RNA modification (other types)
- Chromatin remodeling
dsRBD- dsRNA binding
Z – Zn, DNA binding
R-rich – Arg rich