Post Transcriptional Modifications

POST-TRANSCRIPT MODIFICATION

Post-transcriptional modification:

1. RNA is formed from DNA by the process of transcription.
2. The step involved in protein biosynthesis is a post-translational modification (PTM).
3. There is the generation of proteins when polypeptide chains are formed from the ribosomes' mRNA.

The three post-transcriptional modifications are as follows:

1. Splicing: This involves the removal of the part of the gene that does not code for any protein (introns) and the joining of all the coding genes (exons) to form a functional gene.
2. Capping: This involves the addition of nucleotide methylguanosine triphosphate to the 5'-phosphate end of the mRNA. It guides the mRNA safely to the cytoplasm upon its exit from the nucleus.
3. Tailing: This involves the addition of poly-adenosine residues to the 3'-end of the mRNA.

 

 

 

Certainly! Let's explore the concept of "post-transcriptional modification" as if I were your experienced teacher explaining it to you and your fellow students.

 

 

   Post-Transcriptional Modification: Unveiling the Genetic Recipe Refinement Process

Okay, today we're going to dive into the fascinating world of post-transcriptional modification. You've probably heard about how our genes contain the instructions for making proteins, but what you might not know is that the genetic recipe isn't quite ready for use right after transcription. That's where post-transcriptional modification comes into play.

Transcription Recap:

Before we delve into post-transcriptional modification, let's briefly review transcription. This is the process where our DNA, the genetic code, is "read" by an enzyme called RNA polymerase to create a copy of a specific gene's instructions. This copy is called mRNA (messenger RNA).

So, What Is Post-Transcriptional Modification?

Imagine that you've just written a draft of an important essay, and now you want to make it perfect before you turn it in. Post-transcriptional modification is like the editing and refining process for the genetic recipe contained in the mRNA.

 

 

Key Steps in Post-Transcriptional Modification:

1. Capping: To make sure the mRNA doesn't degrade too quickly, we add a "cap" to the beginning of the mRNA. This cap also helps in guiding the mRNA out of the cell's nucleus.
2. Polyadenylation: At the other end of the mRNA, we add a long chain of "A" nucleotides, called a poly-A tail. This tail also helps in stabilizing the mRNA and guiding it through the cell.
3. Splicing: The genetic recipe in mRNA contains instructions for making various parts of a protein called exons and non-coding regions called introns. In splicing, we cut out the introns and splice together the exons. It's like taking out all the unnecessary sentences in your essay and arranging the important ones in the right order.
4. RNA Editing: Sometimes, the genetic recipe needs a little more tweaking. Through RNA editing, we can actually change the sequence of nucleotides in the mRNA, which can create a slightly different protein from the original genetic instructions.

 

Why Is Post-Transcriptional Modification Important?

• Stability: The modifications make sure the mRNA is stable and can survive its journey from the cell nucleus to the ribosomes, where it's used to make proteins.
• Diversity: RNA editing can generate different versions of proteins from the same gene, adding a layer of diversity to our genetic recipes.
• Accuracy: Splicing helps ensure that the right parts of the genetic recipe are used to create the correct protein.

Examples of Post-Transcriptional Modification:

One of the most well-known examples is alternative splicing in humans. This process can create multiple versions of a protein from a single gene. It's like using the same set of ingredients to make different dishes by rearranging them in various ways.

Conclusion:

In the world of genetics, post-transcriptional modification is where the fine-tuning and polishing of genetic instructions happen. It's like the editing and refining process that ensures our genetic recipes are not only stable but also versatile, accurate, and ready for protein production. It's a crucial step in the complex journey from genes to traits.

 

 

                                                      CAPPING

Capping in Molecular Biology: Protecting and Guiding the Genetic Message

Today, we're going to explore the fascinating world of capping, a crucial process that occurs in molecular biology to protect and guide the genetic message contained in messenger RNA (mRNA).

What Is Capping?

Imagine you're writing a letter to someone, and at the top of the letter, you place a seal with your name and a date. This seal not only identifies you as the author but also ensures the letter doesn't get damaged or lost during its journey. In a similar way, capping is like placing a protective seal at the beginning of an mRNA molecule.

The Key Steps of Capping:

1. Addition of the 5' Cap: During transcription, when the mRNA molecule is being synthesized, a special chemical modification called the 5' cap is added to the beginning of the mRNA. This cap is made up of a modified nucleotide called 7-methylguanosine, and it forms a protective structure at the mRNA's starting point.
2. Importance of the 5' Cap: Now, why is this cap so important? Think of it as a hat for your genetic message. This cap has several crucial functions:
• Protection: It protects the mRNA from being degraded by enzymes that could otherwise break it down. Without this cap, the mRNA would be quite fragile.
• Guidance: The cap helps guide the mRNA out of the cell's nucleus, where transcription takes place, and into the cell's cytoplasm, where it will be used to make proteins. It's like a little flag that says, "I'm ready to go!"
• Initiation of Translation: When the mRNA reaches the ribosome in the cytoplasm, this cap is recognized as the starting point for protein synthesis. It's the equivalent of a green light for the ribosome to begin reading the genetic message.

Why Is Capping Important?

• Stability: Capping stabilizes the mRNA and ensures it can safely navigate the journey from the nucleus to the ribosome without getting damaged.
• Regulation: The cap also plays a role in regulating the translation of the mRNA into protein. It helps ensure that protein synthesis begins at the right place on the mRNA.
• Protection: Without the cap, mRNA would be susceptible to degradation by cellular enzymes. Capping provides a protective shield for the genetic message.

 

 

Diagrams for understanding

 

Examples of Capping:

Capping is a fundamental process in the biology of all eukaryotic organisms, including humans. It's one of the early modifications that occur during mRNA processing.

Conclusion:

In the intricate world of molecular biology, capping is the protective and guiding mechanism that ensures the genetic message contained in mRNA remains intact, secure, and ready for translation into proteins. It's a bit like placing a signature seal on a letter before sending it out into the world.

 

 

 

Polyadenylation: Tailing the Genetic Message for Stability and Transport

Today, we're going to delve into the intriguing process of polyadenylation in molecular biology. Polyadenylation is like adding a tail to the end of a sentence, but in this case, it's the tail end of an mRNA molecule. Let's break down what it is and why it's so important.

What Is Polyadenylation?

Imagine you've just finished writing a letter, and at the end, you decide to add your signature and the date. This signature not only identifies you as the author but also ensures the letter doesn't get lost or damaged during its journey. In the world of molecular biology, polyadenylation is like adding a protective signature, or tail, to the end of an mRNA molecule.

The Key Steps of Polyadenylation:

1. Poly-A Tail Addition: During transcription, when the mRNA molecule is being synthesized, a series of adenine (A) nucleotides (200 – 250 numbers) is added to the end of the mRNA. This results in what's known as a "poly-A tail."
2. Importance of the Poly-A Tail: So, why is this tail so important? Just like the 5' cap, it serves several crucial functions:
• Stability: The poly-A tail provides stability to the mRNA. Without this tail, the mRNA would be more vulnerable to degradation by cellular enzymes that could otherwise break it down.
• Transport: The poly-A tail helps guide the mRNA out of the cell's nucleus, where transcription takes place, and into the cell's cytoplasm, where it will be used to make proteins. It's like a signature that says, "I'm ready to go!"
• Regulation: The length of the poly-A tail can influence the translation of the mRNA into protein. In some cases, it acts as a regulatory element, controlling the timing and efficiency of protein synthesis.

Why Is Polyadenylation Important?

• Stability: Just like capping, polyadenylation helps stabilize the mRNA, ensuring it can safely journey from the nucleus to the ribosome in the cytoplasm without being broken down.
• Guidance: It plays a crucial role in guiding the mRNA out of the nucleus and into the cytoplasm, where the translation of its genetic message into a protein will occur.
• Regulation: The poly-A tail can be involved in controlling the translation process, influencing how quickly and efficiently the genetic message is turned into a protein.

 

 

Examples of Polyadenylation:

Polyadenylation is a fundamental process in the biology of all eukaryotic organisms, including humans. It's a key step during mRNA processing, ensuring the stability, transport, and regulation of genetic messages.

Conclusion:

In the intricate world of molecular biology, polyadenylation is the process of adding a protective tail to the end of an mRNA molecule. This tail enhances the mRNA's stability, guides it to its destination, and, in some cases, helps control when and how its genetic message is translated into a protein. It's like adding a signature and a date at the end of a well-crafted letter before sending it on its journey.

Top of Form

 

Importance:

There are so many enzymes involved In this process:

1.     Cleavage and Polyadenylation Specificity Factor (CPSF)

2.     Cleavage Stimulating Factor (CSF)

3.     Cleavage Factor (CF) [CF1 and CF2] ----- Endonuclease

4.     Poly A Polymerase (PAP)

5.     Polyadenylate Binding Protein (PABP)

 

Sequences:

·       CPSF : AAUAAA

·       CSF : GU BOX

·       CF : CA

 

Role of Polyadenylation:

1.     Virtually all eukaryotic mRNAs are found with a Poly A Tail of 200 to 250 nucleotide length towards its 3’ site.

2.     The event is also called Cleavage and Polyadenylation as a new 3’ end is created, and the Poly A tail is added.

3.     It’s an enzymatically carried out event which ceases the participation of CPSF, CSTF, CF1 and CF2, PAP, and PABP in a sequential manner.

4.     PAP is an enzyme which is a completely independent polymerase that can produce a Poly A Tail.

5.     PABP on another hand ensures that the Poly A tail achieves the desired land. PABP also plays an important role during translation as it attacks itself in the tail and is transported in the cytoplasm.

 

6.    The key functions of the Polyadenylation are:

a.     Protection of mRNA from the cellular enzymatic degradation.

b.     Helps in the transport of mRNA through the nucleus.

c.      It serves as a recognition sequence for binding of translation factors during initiation phase of protein translation.

 

 

 

 

 

 

SPLICING

 

1.    In simple words:

a.     Removing the non-coding area.

b.     Retaining the coding area.

 

2.    Coding & Non-Coding Area:

a.     In a eukaryotic mRNA there are coding and non-coding area.

b.     Non-coding regions   :           Introns

c.      Coding regions           :           Exons

d.     At last exons are being submerged.

 

3.    

4.    Splicing Mechanism:

a.     GU ---- AG

b.     AU ---- AC

 

 

 

 

5.     RNA Splicing- Definition, process, mechanism, types, errors, uses (microbenotes.com)

 

SPLICING

 

Splicing: Piecing Together the Genetic Puzzle

Today, we're going to embark on a journey into the intricate world of splicing in molecular biology. Splicing is like putting together a jigsaw puzzle, but instead of pictures, we're assembling pieces of genetic information. Let's delve into what splicing is, why it's crucial, and how it works.

What Is Splicing?

Think of your genetic code, your DNA, as a long string of letters. Each of these letters represents a specific instruction for making a part of a protein. However, here's the twist: not all of these instructions are needed all the time. So, splicing is the process of carefully cutting out the unnecessary parts and piecing together the essential instructions.

The Key Steps of Splicing:

1. Introns and Exons: In your genetic code, you have regions known as exons, which are like the essential sentences of a story, and introns, which are like the extra, unneeded words. Splicing focuses on exons while eliminating introns.
2. Cutting and Pasting: Imagine you're editing a story, and you decide to cut out a paragraph that's not essential. In splicing, specialized molecular machines cut out the introns and paste together the exons. This precision editing happens while the mRNA (messenger RNA) is being created during transcription.

Importance of Splicing:

Splicing is not just about simplifying the genetic code. It has several important functions:

• Diversity: Splicing allows one gene to code for multiple versions of a protein. It's like having different flavors of ice cream using the same basic ingredients but in different combinations.
• Regulation: It helps in regulating which parts of the genetic code are used. Think of it as having control over which chapters of a book you want to read.
• Efficiency: Splicing ensures that only the necessary instructions are included in the final mRNA. This is like having a concise and efficient set of instructions for building a protein.

Why Is Splicing Important?

• Variety: Splicing contributes to the diversity of proteins in our bodies. It allows one gene to have multiple functions by producing various protein versions.
• Precision: Splicing ensures that the right parts of a gene's instructions are used at the right time and place. This precision is critical for proper protein function.

Examples of Splicing:

Splicing is a fundamental process in eukaryotic organisms, including humans. It plays a significant role in creating protein diversity and ensuring that our genetic instructions are used efficiently.

Conclusion:

In the intricate world of molecular biology, splicing is the precision editing process that assembles the essential instructions from our genetic code while eliminating unnecessary parts. It's like crafting a unique story by carefully selecting the right sentences from a sea of words. Splicing is a fundamental mechanism that underlies the complexity and diversity of proteins in living organisms.

 

SPLICING APPARATUS: THE MOLECULAR MACHINERY BEHIND GENETIC EDITING

 

Today, students, we're going to explore the intriguing world of the splicing apparatus, the molecular machinery responsible for the intricate process of genetic editing known as splicing. Just like assembling a complex machine, splicing requires a set of tools and components. Let's uncover what the splicing apparatus is, how it works, and why it's vital in the world of molecular biology.

What Is the Splicing Apparatus?

Think of the splicing apparatus as a team of specialized workers, each with a specific task, coming together to edit and refine the genetic code within an mRNA molecule. Their job is to cut out unnecessary parts and assemble the critical instructions for making a protein.

Key Components of the Splicing Apparatus:

1. Small Nuclear Ribonucleoproteins (snRNPs): These are like the foremen of the splicing apparatus. They consist of small RNA molecules (snRNA) combined with proteins. They recognize the boundaries between exons and introns and guide the splicing process.
2. Spliceosome: The spliceosome is the central assembly of the splicing apparatus. It's like the master architect. It's made up of snRNPs, additional proteins, and the mRNA itself. The spliceosome precisely cuts out introns and joins exons, ensuring that the final mRNA contains the right instructions.
3. Branch Point Sequence: Think of this as the hidden clue in the genetic code. It's a specific sequence within the intron that guides the spliceosome on where to make the cut.
4. Exon-Exon Junction Complex (EJC): Once the spliceosome does its work, the EJC marks the junction between exons. It's like placing a bookmark in a book to remember where you left off.

 

How Does the Splicing Apparatus Work?

Imagine you're a team of skilled editors working on a manuscript, carefully cutting out unnecessary paragraphs and arranging the essential parts in the right order. The splicing apparatus performs a similar task, but with genetic instructions.

Here's how it works:

1. Recognition: The splicing apparatus, guided by snRNPs, identifies the boundaries between exons and introns in the pre-mRNA.
2. Cutting and Pasting: The spliceosome makes precise cuts at the intron-exon boundaries, just as an editor would remove unneeded sentences. It then pastes together the exons, ensuring they are in the right order.
3. Junction Marking: The EJC marks the newly joined exon-exon junctions. This marking helps ensure the mRNA is correctly processed and transported to the ribosome for protein synthesis.

Importance of the Splicing Apparatus:

The splicing apparatus plays a crucial role in molecular biology for several reasons:

• Diversity: It enables one gene to produce multiple protein variants, increasing the diversity of proteins in an organism.
• Regulation: The splicing apparatus helps regulate when and how specific genetic instructions are used.
• Precision: It ensures that the right parts of the genetic code are included in the final mRNA for efficient protein production.

Examples of the Splicing Apparatus:

The splicing apparatus is an essential component of the splicing process in all eukaryotic organisms, including humans. It contributes to the complexity and diversity of proteins in our bodies.

Conclusion:

In the intricate world of molecular biology, the splicing apparatus is the molecular machinery responsible for precisely editing and refining genetic instructions within an mRNA molecule. It's like a team of skilled editors working together to ensure that the final manuscript, in this case, the mRNA, contains the right sentences in the right order. Splicing is a fundamental process underlying the diversity and precision of protein production in living organisms.

 

 

 

 

 

RNA EDITING

RNA Editing: Rewriting the Genetic Script

Today, we're going to delve into the intriguing world of RNA editing in molecular biology. RNA editing is like being a genetic scriptwriter, making changes to the storyline of our genetic code. Let's uncover what RNA editing is, how it works, and why it's a fascinating and important process in the world of genetics.

What Is RNA Editing?

Imagine you've written a story, but upon review, you decide to change a few words or sentences to improve it. RNA editing is similar but at the genetic level. It's the process of altering the genetic script contained in mRNA (messenger RNA) to create a slightly different version of a protein from the original genetic instructions.

The Key Types of RNA Editing:

1. Substitution Editing: This is like finding a better word to use in your story. In substitution editing, specific nucleotides in the mRNA are changed, often by swapping one nucleotide for another.
2. Insertion Editing: Imagine adding an extra sentence or phrase to your story for clarification. Insertion editing involves adding extra nucleotides into the mRNA sequence.
3. Deletion Editing: In this case, you're removing sentences or words from your story. Deletion editing entails the removal of specific nucleotides from the mRNA.

How Does RNA Editing Work?

Here's how RNA editing works:

1. Recognition: The RNA editing machinery identifies specific sites in the mRNA where editing is needed. These sites are often indicated by particular sequences or structures in the mRNA.
2. Editing Enzymes: Specialized enzymes, like editors with red pens, perform the changes. These enzymes can substitute one nucleotide for another, add new nucleotides, or remove existing ones.
3. Final mRNA: The result is a modified mRNA with changes to the genetic code. This edited mRNA is then used as a template for protein synthesis.

Importance of RNA Editing:

RNA editing serves several crucial roles in molecular biology:

• Diversity: It greatly enhances the diversity of proteins that an organism can produce from a limited set of genes. It's like having multiple versions of a story with slightly different plots.
• Fine-Tuning: RNA editing allows for fine-tuning of protein function, adapting it to specific needs in different tissues or under various conditions.
• Adaptation: It can adapt to changing environmental conditions and cellular requirements by altering the protein's properties.

Why Is RNA Editing Important?

• Protein Diversity: RNA editing contributes significantly to the diversity of proteins in higher organisms, like humans, with relatively fewer genes compared to the vast number of proteins they can produce.
• Precision: It's a way of precisely tailoring the genetic script to meet the specific needs of different cells and tissues.

Examples of RNA Editing:

RNA editing is widespread in eukaryotic organisms, including humans. One well-known example is the editing of the neurotransmitter receptor in the brain, which affects the way nerve cells communicate.

Conclusion:

In the intricate world of molecular biology, RNA editing is the process of making changes to the genetic script contained in mRNA. It's like being a genetic scriptwriter, rewriting the story to create diversity, fine-tune protein function, and adapt to changing needs. RNA editing is a fundamental mechanism that underlies the complexity and adaptability of protein production in living organisms.