RNA editing
RNA editing is a molecular process through which some cells can make discrete changes to specific nucleotide sequences within a RNA molecule after it has been generated by RNA polymerase. RNA editing is relatively rare, and common forms of RNA processing (e.g. splicing, 5'-capping and 3'-polyadenylation) are not usually included as editing.
Does RNA editing occur in all organisms?
It occurs in all living 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.
What is the reference book for RNA editing in plants?
"RNA editing in plant organelles". RNA Editing (Benne, R., Ed.), Ellis Harwood, New York. ^ Malek O, Lättig K, Hiesel R, Brennicke A, Knoop V (March 1996). "RNA editing in bryophytes and a molecular phylogeny of land plants".
Can RNA editing be done in kinetoplasts?
RNA editing through the addition and deletion of uracil has been found in kinetoplasts from the mitochondria of Trypanosoma brucei Because this may involve a large fraction of the sites in a gene, it is sometimes called "pan-editing" to distinguish it from topical editing of one or a few sites.
Types of changes
Origin and evolution of RNA editing
RNA editing may be involved in RNA degradation
Does RNA editing occur in the cytoplasm of the cell?
RNA editing occurs in the cytoplasm of the cell. What are two explanations for why some RNA molecules are cut and spliced? It makes it possible for a single gene to produce several different forms of RNA.
How does RNA editing occur?
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 living organisms and is one of the most evolutionarily conserved properties of RNAs.
Which organelle is responsible for RNA editing?
mitochondriaRNA editing mainly occurs in the mitochondria and plastids in plants. The conversion of C-to-U is the main form of RNA editing in plants. This editing phenomenon was described in 1989 in wheat mitochondria (Covello and Gray, 1989).
Does RNA editing occur in eukaryotes?
RNA editing is widely observed in eukaryotic organisms and their viruses. Editing, like splicing, represents a form of processing that has the capacity to amplify genetic diversity and alter gene product function by modifying the information transfer process at the posttranscriptional level.
Where does the transcription take place?
The process of Transcription takes place in the cytoplasm in prokaryotes and in nucleus in eukaryotes. It uses DNA as a template to make an RNA (mRNA) molecule. During transcription, a strand of mRNA is made that is complementary to a strand of DNA.
Where in the cell does transcription take place?
With the genes bound in the nucleus, transcription occurs in the nucleus of the cell and the mRNA transcript must be transported to the cytoplasm.
What is mRNA editing in transcription?
Such editing events alter the coding properties of mRNA.RNA editing can be generally defined as the co- or post transcriptional modification of the primary sequence of RNA from that encoded in the genome through nucleotide deletion, insertion, or base modification mechanisms.There are two pathways of RNA editing: the ...
Where does translation take place in the?
Where Translation Occurs. Within all cells, the translation machinery resides within a specialized organelle called the ribosome. In eukaryotes, mature mRNA molecules must leave the nucleus and travel to the cytoplasm, where the ribosomes are located.
What happens RNA editing quizlet?
RNA editing refers to the process in which the information content within the RNA is altered by virtue of a chemical change in the base make up.
How is RNA modified after transcription in eukaryotes?
RNA Transport from the Nucleus to the Cytoplasm Post-transcriptional modifications of pre-mRNA, such as capping, splicing, and polyadenylation, take place in the nucleus. After these modifications have been completed, the mature mRNA molecules have to be translocated into the cytoplasm, where protein synthesis occurs.
How is RNA modified after transcription in eukaryotic cells?
In splicing, some sections of the RNA transcript (introns) are removed, and the remaining sections (exons) are stuck back together. Some genes can be alternatively spliced, leading to the production of different mature mRNA molecules from the same initial transcript.
How is mRNA modified in eukaryotes?
Eukaryotic pre-mRNAs are modified with a 5′ methylguanosine cap and a poly-A tail. These structures protect the mature mRNA from degradation and help export it from the nucleus. Pre-mRNAs also undergo splicing, in which introns are removed and exons are reconnected with single-nucleotide accuracy.
What is RNA editing?
RNA editing. RNA editing refers to a modification of RNA that changes how the sequence is read so that it is different from DNA. The most well studied in animals is adenosine deaminase acting on RNA (ADAR) mediated A-to-I RNA editing [168]. ADAR1 and ADAR2 are ubiquitously expressed and contain catalytic activity, ...
What is the main form of RNA editing in mammals?
A-to-I RNA editing (deamination of adenosine to inosine) is the main form of RNA editing in mammals, which occurs in regions of double-stranded RNA (dsRNA). Adenosine deaminases acting on RNAs (ADARs) are the RNA-editing enzymes involved in the hydrolytic deamination of A-to-I editing [89].
What is the process of converting RNA to cDNA?
The process of converting RNA to cDNA creates a “G” where inosine is inserted on the RNA fragment, while the corresponding fragment on the DNA should read as an “A.” Very deep sequencing is needed to rule out the mismatches from PCR, sequencing errors, pseudogenes, duplicated regions, or polymorphisms in the genome.
What is the most common form of RNA editing?
In humans, deamination of adenosine is the most common form of RNA editing. I pairs with C instead of U. The conversion is carried out by ADAR (adenosine deaminase acting on RNA) enzymes. The ADAR protein contains double-stranded RNA-binding domains (dsRBDs) and a C-terminal deaminase domain.
Why is genome plasticity important?
Thus further genome plasticity-related studies are needed to explore the complex interactions of genetic, epigenetic, and environmental factors in the pathogenesis of diseases. Further investigations are also required to find more disease-related genetic and epigenetic modifications, including genome variation and CNV, DNA methylation, noncoding RNA and RNA editing, and centromere and telomere dynamics.
What enzyme converts adenosine to inosine?
The enzyme ADAR acts on dsRNA to convert adenosine to inosine, which is read as guanosine, mostly in UTRs, miRNA precursors, and retrotransposons [168]. Not to be confused with adenosine deaminase tRNA specific (ADATs), which specifically act on tRNA [168]. C-to-U editing also occurs but is less common.
Which enzymes are known to flip bases?
Several nucleic acid modifying enzymes, such as DNA glycosylases, are also known to utilize the base-flipping mechanism for their action. Nevertheless, unlike these enzymes which act on bases located in distorted duplex structures, ADAR interacts with specific adenosines within normal base-paired duplex.
Where does RNA editing occur?
RNA editing, a type of RNA processing, was first discovered by Benne and co-workers in a mitochondrion-encoded mRNA of a kinetoplastid trypanosome.1 The term RNA editing initially referred only to the process as it occurs in trypanosomes, which involves the post-transcriptional insertion and deletion of uridylate (UMP) within nascent transcripts.
What is RNA editing?
RNA editing is the posttranscriptional modification of an RNA nucleotide sequence at one or more positions. There are two general types of RNA editing, viz., substitution editing, and insertion/deletion editing. RNA editing of either type leads to the formation of transcripts whose sequence differs from that of the genome template. Such RNA sequence differences between mature transcript and encoding genome represent a form of genetic recoding. The sequence changes generated by RNA editing are different from those arising from 5′-capping, 3′-polyadenylation, and splicing, additional RNA processing events that occur during mRNA biogenesis in eukaryotes. RNA editing is widely observed in eukaryotic organisms and their viruses. Editing, like splicing, represents a form of processing that has the capacity to amplify genetic diversity and alter gene product function by modifying the information transfer process at the posttranscriptional level.
What are the factors that regulate RNA editing?
C-to-U apoB RNA editing is regulated by a range of factors including developmental, nutritional, environmental, and metabolic stimuli.
How are ADAR genes conserved?
ADAR editing enzymes are found in all multicellular animals and are conserved in sequence and protein organization. The number of ADAR genes differs between animals, ranging from three in mammals to one in Drosophila. ADAR is also alternatively spliced to generate isoforms that can differ significantly in enzymatic activity. Therefore, to study the enzyme in vitro, it is essential to have an easy and reliable method of expressing and purifying recombinant ADAR protein. To add to the complexity of RNA editing, the number of transcripts that are edited by ADARs differs in different organisms. In humans there is extensive editing of Alu sequences, whereas in invertebrates transcripts expressed in the central nervous system are edited and this editing increases during development. It is possible to quantify site‐specific RNA editing by sequencing of clones derived from RT‐PCR products. However, for routine assaying of an edited position within a particular transcript, this is both expensive and time consuming. Therefore, a nonradioactive method based on poison primer extension assay is an ideal alternative.
Is RNA editing a prokaryote?
To date, RNA editing has not been observed in a prokaryote. Typically, RNA editing reactions are put into two broad catagories based on their reaction mechanisms. One type, insertion/deletion RNA editing, involves the insertion or deletion of nucleotides and actually changes the length of the target RNA. The second type, RNA editing by base ...
Is it possible to study the enzyme in vitro?
Therefore, to study the enzyme in vitro, it is essential to have an easy and reliable method of expressing and purifying recombinant ADAR protein. To add to the complexity of RNA editing, the number of transcripts that are edited by ADARs differs in different organisms.
Is there editing of Alu?
In humans there is extensive editing of Alu sequences, whereas in invertebrates transcripts expressed in the central nervous system are edited and this editing increases during development . It is possible to quantify site‐specific RNA editing by sequencing of clones derived from RT‐PCR products.
Where does RNA editing occur?
A common example of addition and deletion RNA editing occurs in the protozoan organism trypanosomes, one of which causes the infection of African sleeping sickness. Scientists have extensively investigated RNA editing mechanisms in the mitochondrial DNA in these organisms.
How does RNA editing work?
Some cells alter the mRNA in a process known as RNA editing. RNA editing is the process of modifying RNA nucleotides to change the amino acid sequence. This usually involves editing specific nucleotides and is considered a separate process than the RNA splicing that occurs in eukaryotes, which is more like a large scale cut and paste type of edit.
What is the name of the substitution that produces adenosine to inosine?
This type of substitution is called deamination because the adenine nucleotide loses a chemical group called an amine group. Deamination produces an adenosine to inosine substitution, one of the most common substitutions in RNA editing.
Why is RNA editing important?
RNA editing can be used to modify the proteins made based on the conditions in the cell. It helps create diversity in protein products from a limited number of genes. Many types of cells from single-celled protozoa all the way to humans perform RNA editing.
How can RNA be edited?
The first way that RNA can be edited is through addition. In addition editing, new nucleotides are inserted into the original sequence. Imagine taking your cursor and choosing a spot to add a new letter when typing a message. This is an example of an addition.
What happens when you add a nucleotide in the middle of a sequence?
If you add a nucleotide in the middle of a sequence, everything downstream gets shifted over one, effectively changing the reading frame for the rest of the protein. Similarly, a deletion, or removal of a nucleotide, can also cause a frameshift.
What is the purpose of a guide RNA?
A ''guide'' RNA is created by the cell to help place the insertions and deletions in the right place. A group of proteins called the editosome then align the guide with RNA and add or delete bases as needed. Guide RNA has been shown to help organize additions and deletions in trypanosome mitochondrial RNA. 2.
