A-to-I RNA Editing

Relevance: GS III, Science and Technology, Biotechnology

What Happened?
 

1. Recently, Researchers from China have found that cells sometimes change their RNA instructions after copying them from DNA.
2. This change is known as A-to-I RNA editing.
3. This strange behavior has been found in a fungus called Fusarium graminearum.
4. This fungus infects wheat and barley crops.

What is the Cell? A cell is the smallest basic unit of life that makes up all living organisms. It serves as the structural and functional building block of life, capable of independent replication. Each cell is enclosed by a membrane and contains a fluid called cytoplasm, where various molecules and specialized structures called organelles are found. These organelles perform specific tasks essential for the cell’s survival and function. Out of several organelles Nucleus is the one of the most important organelles which contains genetic material in itself like Deoxyribose Nucleic Acid (DNA) and Ribonucleic Acid (RNA)

What is Deoxyribonucleic Acid (DNA)?

1. DNA stands for Deoxyribonucleic Acid.
2. It carries the instructions that help living things grow, work, and stay alive.
3. DNA looks like a twisted ladder. This shape is called a double helix model.
4. The sides of the ladder are made of sugar called deoxyribose and phosphate.
5. The steps of the ladder are made of four special parts called bases. These bases are:
   1. Adenine (A)
   2. Thymine (T)
   3. Cytosine (C)
   4. Guanine (G)
6. These bases always pair in a special way:
   1. A pairs with T
   2. C pairs with G
7. The order of these bases is like a code.
8. This code gives the body instructions to make proteins and RNA.
9. DNA is found in almost every cell of a living thing.
10. It is passed from parents to children, which is why family members can look alike.

What is Ribonucleic Acid (RNA)?

1. RNA stands for Ribonucleic Acid.
2. It is found in all living cells.
3. RNA is similar to DNA, but not exactly the same.
4. RNA is usually single-stranded, not double stranded like DNA.
5. The backbone of RNA is made of phosphate and a sugar called Ribose.
6. RNA has four bases:
   1. Adenine (A)
   2. Uracil (U) (This replaces Thymine (T) in DNA)
   3. Cytosine (C)
   4. Guanine (G)
7. There are different types of RNA in the cell:
   1. mRNA (messenger RNA): It carries instructions to make proteins.
   2. rRNA (ribosomal RNA): It helps make the parts of the cell where proteins are built.
   3. tRNA (transfer RNA): It brings the building blocks to make proteins.
8. Some RNA helps to control which genes are turned on or off.
9. Some viruses, like the flu or coronavirus, use RNA as their genetic material instead of DNA.

What is Transcription?

1. Transcription is the process where a DNA is copied to make a RNA molecule, called messenger RNA (mRNA).
2. An enzyme called RNA polymerase starts this process.
3. This process uses one strand of DNA as a guide.
4. The mRNA when formed it moves into the cytoplasm, where it helps to make proteins.
5. It follows the complementary base-pairing rule, but adenine pairs with uracil (U) in RNA instead of thymine (T).
6. Only a specific segment of DNA is transcribed, not the entire DNA like in replication.

 

Features	mRNA (Messenger RNA	tRNA (Transfer RNA)	rRNA (Ribosomal RNA)
Structure	Linear, single-stranded	Cloverleaf shape	Complex, spherical
Function	Carries genetic code from DNA to ribosomes	Brings amino acids to ribosome for protein making	Forms the core of ribosomes, helps protein synthesis
Length	300–12,000 nucleotides (in mammals)	76–90 nucleotides	Varies (different sizes in ribosome subunits)
Location of Synthesis	Nucleus	Cytoplasm	Ribosomes
Role in Protein Synthesis	Provides the template (codons) for building proteins	Matches its anticodon to mRNA codons, delivers amino acids	Helps assemble ribosome and catalyzes peptide bond formation

 

What is A-to-I RNA Editing?

1. It is also known as the Adenosine-to-Inosine RNA editing. It is a natural process that changes the information in RNA after it is made from DNA.
2. The Adenosine (A) in the RNA molecule is chemically converted into Inosine (I).
3. This editing is carried out by enzymes called ADARs (Adenosine Deaminases Acting on RNA).
4. ADAR enzymes recognize double-stranded regions of RNA and change specific adenosines (A) into inosines (I).
5. Inosine is recognized as guanosine (G) by the cellular machinery during translation (process of converting the genetic information encoded in mRNA into a protein) and other processes, which can alter the amino acid sequence of proteins.

DNA → Transcription → mRNA → A-to-I Editing → Modified mRNA → Translation → Protein

Significance of A-to-I RNA Editing:

1. Creates More Protein Types from One Gene: A-to-I RNA editing helps the body make different kinds of proteins from the same gene. This means the body can do many different jobs without needing extra genes.
2. Very Important for the Brain: In the human brain, A-to-I editing helps produce different forms of neurotransmitter receptors by modifying the mRNA sequence. This is important for memory, learning, and overall brain function.
3. Supports the Immune System: A-to-I editing helps the body tell the difference between its own cells and viruses. This prevents the immune system from attacking healthy cells by mistake.
4. Useful for Treating Diseases: Scientists are looking at how A-to-I editing can help treat diseases like cancer, brain disorders, and genetic problems. It offers a new way to fix mistakes in RNA without touching the DNA.
5. Nervous System Development: A-to-I RNA editing is important for the development of the nervous system. It also plays a key role in the overall growth and development of the body.