RNA EDITING
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TABLE OF CONTENT
1. Introduction
2. Mechanisms Of RNA Editing
3. Functions Of RNA Editing
4. Recent Research On RNA Editing
5. Major strengths and weaknesses of RNA Editing
6. Future perspectives
7. Challenges in RNA Editing
8. Conclusion
9. References
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INTRODUCTION
RNA editing (also RNA modification) is a molecular process through which some
cells can make discrete changes to specific nucleotide sequences within
an RNA molecule after it has been generated by RNA polymerase.
• It occurs in all organisms and is one of the
most evolutionarily conserved properties of RNAs.
• RNA editing may include the
insertion, deletion, and base substitution
of nucleotides within the RNA molecule.
• RNA editing is relatively rare and
can affect the stability of RNAs and
has been linked with human diseases.
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A MILESTONE OF THE DISCOVERY
OF RNA EDITING
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MECHANISMS OF RNA EDITING
1. SITE-SPECIFIC DEAMINATION EDITING
A(adenosine) to I(inosine) double-stranded mechanism
• occurs in viruses, humans
C(cytidine) to U(uridine) and U to C
• occurs in the chloroplast, plant mitochondria, and human genes.
2. GUIDE RNA-MEDIATED SITE-SPECIFIC INSERTION AND
DELETION OF URIDINE
U insertion /deletion
• Occurs in Kinetoplasts(networks of circular DNA molecules present in
mitochondria)
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SITE-SPECIFIC DEAMINATED EDITING
Site-specific Deamination of Cytidine and Adenosine:
Cytidine Uridine
Cytidine
deaminase
Adenosine Inosine
ADAR
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 Occur in APO-B Gene
 Unedited Gene -APO-B 100 Protein ( Liver)
 Edited Gene- APO-B 48 Protein ( Intestine )
 Enzyme ADAR ( ds binding Domains)
 Inosine can base pair with any nitrogenous
base pair it may be A T C G
 It detected as Guanosine during translation
process.
 This conversion acting on dsRNA
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Guide RNA mediated site-specific insertion
and deletion of uridine
Guide RNA: It is part of degraded introns.
• It is a small fraction of the RNA sequence
That just comes out of the splicing of RNA.
• Guide RNA guide the process of RNA editing
In eukaryotes, that's why called guide RNA.
Step by Step mechanism
• Cleavage of RNA with endonuclease
• Activity of TuTase and addition of uridine
• Ligation of nick using ligase
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FUNCTIONS OF RNA EDITING
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• Three mammalian ADAR genes (ADAR1–3) with common functional domains have
been identified.
• Deficiencies in the A→I RNA editing mechanism cause human diseases and
pathophysiology.
• RNA editing is a major mechanism, although reported exclusively in Eukaryotes.
• RNA editing has been reported in Protozoa, plants, and mammals, nuclear,
mitochondrial, chloroplast, and viral RNAs; mRNA, tRNA, and rRNA and not yet
fungi or prokaryotes;
• Researchers are now exploring a form of editing in prokaryotes and certain viruses.
• A method has been developed by researchers for seeing the RNA editing procedure
in real-time, the repaired strand emits green light, and even for the confirmation of
repair mechanisms.
• However, researches are still ongoing to elucidate key mechanisms of editing in
various organisms.
RECENT RESEARCH ON RNA EDITING
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Major strengths and weakness of RNA
Editing
Major strengths of RNA Editing
1. RE has been integrated into
biological networks
2. Gene expression,
3. RNA editing better than DNA
editing.
4. RNA editing is therefore considered
to be less risky.
Major weakness of RNA Editing
1. How RE activity is globally
regulated is unknown.
2. Many editing sites in human
transcriptomes remain to be
discovered.
3. Monitoring of the global activity of
RE in-vivo is rare.
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Future perspectives of RNA Editing
1. Description of physiological significance of particular editing events
identified in tumor, neuronal tissues and brain or other specialized
organ.
2. Molecular mechanisms on how RE affect the expression or functions
of many genes through the alteration of codon, splice pattern, stability
or localization of protein coding transcripts, modulation of regulatory
RNA biogenesis and function.
3. Monitoring of global activity of RE in-vivo as a useful early
biomarker for patient with disease.
4. Therapeutic applications.
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CHALLENGES IN RNA EDITING
High-throughput sequencing-based approaches are being widely adopted to
answer questions that require a genome-wide approach, such as
• “How many miRNAs are edited?” or
• “How many editing sites are there in the human brain?” or
• “How many editing sites are there in plant mitochondria RNA?”
• The physiological significance of recoding editing of newly discovered protein-
coding genes needs to be identified.
• We need to better understand the significance of the editing of noncoding
repetitive RNAs of transposons and retrotransposons
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CONCLUSION
• RNA editing alters RNA sequence without altering the sequence or integrity of
genomic DNA.
• RNA editing generates RNA and protein diversity in eukaryotes and results in
specific amino acid substitutions, deletions, and changes in gene expression
levels.
• Adenosine-to-inosine RNA editing represents the most important class of editing
in human and affects function of many genes.
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References
1. Chen, Y.-T., I. Y.-F. Chang, C.-H. Kan, Y.-H. Liu, Y.-P. Kuo, H.-H. Tseng, H.-C. Chen,
H. Liu, Y.-S. Chang and J.-S. J. C. Yu (2020). "circRNAome Profiling in Oral
Carcinoma Unveils a Novel circFLNB that Mediates Tumour Growth-Regulating
Transcriptional Response." 9(8): 1868.
2. Hsiao, Y.-H. E., J. H. Bahn, Y. Yang, X. Lin, S. Tran, E.-W. Yang, G. Quinones-Valdez
and X. J. G. r. Xiao (2018). "RNA editing in nascent RNA affects pre-mRNA splicing."
28(6): 812-823.
3. Porath, H. T., E. Hazan, H. Shpigler, M. Cohen, M. Band, Y. Ben-Shahar, E. Y. Levanon,
E. Eisenberg and G. J. N. c. Bloch (2019). "RNA editing is abundant and correlates with
task performance in a social bumblebee." 10(1): 1-14.
4. Small, I. D., M. Schallenberg‐Rüdinger, M. Takenaka, H. Mireau and O. J. T. P. J.
Ostersetzer‐Biran (2020). "Plant organellar RNA editing: what 30 years of research has
revealed." 101(5): 1040-1056.
5. Song, B., Y. Shiromoto, M. Minakuchi and K. J. W. I. R. R. Nishikura (2022). "The role
of RNA editing enzyme ADAR1 in human disease." 13(1): e1665.
6. Tran, S. S., H.-I. Jun, J. H. Bahn, A. Azghadi, G. Ramaswami, E. L. Van Nostrand, T. B.
Nguyen, Y.-H. E. Hsiao, C. Lee and G. A. J. N. n. Pratt (2019). "Widespread RNA
editing dysregulation in brains from autistic individuals." 22(1): 25-36.
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