1. GURU NANAK INSTITUTE OF PHARMACEUTICAL SCIENCE AND
TECHNOLOGY
TOPIC : Processing of mRNA: 5’ cap formation
NAME OF THE STUDENT : ANKIT GHOSH
UNIVERSITY ROLL NUMBER : 31308421036
ACADEMIC SESSION : 2022-2023
PAPER NAME : MOLECULAR BIOLOGY
PAPER CODE : CMC 302
Maulana Abul Kalam Azad University of Technology
2. INTRODUCTION
B. Sc./ SEM 3/2022-23/ / MOLECULAR BIOLOGY / CMC 302 /Presentation_1
In humans and other eukaryotes, a freshly made RNA transcript is not quite ready to go. Instead,
it's called a pre-mRNA and has to go through some processing steps to become a
mature messenger RNA (mRNA) that can be translated into a protein. These include:
•Addition of cap and tail molecules to the two ends of the transcript. These play a protective role,
like a book's front and back covers.
•Removal of "junk" sequences called introns.
3. Overview of pre-mRNA processing in eukaryotes
B. Sc./ SEM 3/2022-23/ / MOLECULAR BIOLOGY / CMC 302 /Presentation_1
In bacteria, RNA transcripts are ready to act as messenger RNAs and get translated
into proteins right away. In eukaryotes, things are a little more complex. The
molecule that's directly made by transcription in eukaryotic cells is called a pre-
mRNA, reflecting that it needs to go through a few more steps to become an actual
messenger RNA (mRNA). These are:
•Addition of a 5' cap to the beginning of the RNA
•Addition of a poly-A tail (tail of A nucleotides) to the end of the RNA
•Chopping out of introns, or "junk" sequences, and pasting together of the remaining,
good sequences (exons)
Once it's completed these steps, the RNA is a mature mRNA. It can travel out of the
nucleus and be used to make a protein.
4. 5' cap formation
B. Sc. / SEM 3/2022-23/ / / MOLECULAR BIOLOGY / CMC 302/Presentation_1
Both ends of a pre-mRNA are modified by the addition of chemical groups. The group at
the beginning (5' end) is called a cap, while the group at the end (3' end) is called a tail.
Both the cap and the tail protect the transcript and help it get exported from the nucleus
and translated on the ribosomes found in the cytosol.
The 5’ cap is added to the first nucleotide in the transcript during transcription. About 20-
40 ribonucleotides have been joined together by RNA polymerase, a group of enzymes
adds a “cap” to the 5’ end of the growing transcript. In this process, a 5’ phosphate is
replaced by modified guanosine that has a methyl group attached to it (7-Methyl
guanosine). The cap is a modified guanine (G) nucleotide, and it protects the transcript
from being broken down. It also helps the ribosome attach to the mRNA and This 5’ cap
helps the cell distinguish mRNA from other types of RNA and plays a role in subsequent
translation.
5. CONCLUSION
SUMMARY
B. Sc./ SEM 3/2022-23/ / MOLECULAR BIOLOGY / CMC 302 /Presentation_1
FUNCTIONS:
• Essential for the growth of eukaryotic cells
• Marks the translational start site
• Protects mRNA from degradation by 5'exoribonucleases Methyl group
facilitate translation
• Participate in mRNA splicing and enhances its accuracy
• Binds to nuclear cap binding complex to facilitate mRNA transport to
cytoplasm
6. REFERENCE
B. Sc. / SEM 3/2022-23/ / MOLECULAR BIOLOGY / CMC 302 /Presentation_1
1. Temperley RJ, Wydro M, Lightowlers RN, Chrzanowska-Lightowlers ZM (June 2010). "Human
mitochondrial mRNAs—like members of all families, similar but different". Biochimica et Biophysica
Acta (BBA) - Bioenergetics. 1797 (6–7): 1081–1085.
2. Monde RA, Schuster G, Stern DB (7 June 2000). "Processing and degradation of chloroplast
mRNA". Biochimie. 82 (6–7): 573–582.
3. Shatkin, A (December 1976). "Capping of eucaryotic mRNAs". Cell. 9 (4): 645–653.
4.Banerjee AK (June 1980). Microbiological Reviews. 44 (2): 175–205.
5.Sonenberg N, Gingras AC (April 1998). "The mRNA 5′ cap-binding protein eIF4E and control of
cell growth". Current Opinion in Cell Biology. 10 (2): 268–275.
