RNA processing prepares transcripts produced from transcription so they can function in protein synthesis. It involves several key steps like capping, splicing, and polyadenylation of mRNA. Capping adds a methylated guanine cap to the 5' end, splicing removes introns from mRNA, and polyadenylation adds an adenine tail to the 3' end. Other RNAs like tRNA and rRNA also undergo processing to become mature and functional, which involves cleavage, addition of modified bases, and assembly of ribosomal subunits. RNA processing is essential for generating diverse and properly functioning mRNAs and other RNAs to regulate gene expression and maintain cellular functions.

1. RNA
PROCESSING
SUBMITTED BY :-
Ankita Sunani
Registration no:22MSZOLG49

2. WHAT IS RNA PROCESSING?
• RNA processing prepares the transcript (the product of
transcription) so it can function in translation or protein
synthesis. As such, it takes place after transcription and
before translation.
• When it is newly formed and unprocessed, “pre-” is
attached to the name of the transcript: pre-mRNA, pre-
tRNA, and pre-rRNA. After processing, the transcript is said
to become “mature”, meaning it is ready for protein
synthesis.

4. TYPES OF RNA INVOLVED IN RNA
PROCESSING
 Messenger RNA (mRNA): produced during transcription,
this molecule contains the protein information of the gene
that was encoded in DNA and will be used as a template
in translation.
 Transfer RNA (tRNA): decodes mRNA into a protein
during translation.
 Ribosomal RNA (rRNA): makes up the core of the
ribosome, the organelle in which protein synthesis takes
place.

5. STEPS INVOLVED IN RNA PROCESSING
It involves several steps, including capping, splicing, and
polyadenylation.

6. CAPPING:
• This is the first processing event an mRNA undergoes before translation. Capping is
the process of adding a 7-methylguanosine cap to the 5’ end of the primary
transcript by phosphate linkage.
• Three enzymes are involved in this process – 7-methyltransferase, RNA
triphosphatase and guanylyltransferase.
• The process of capping is initiated by the removal of phosphate groups from the
terminal nucleotide to create a site for the addition of the methylated guanine
residues.
• Guanylyltransferase first adds guanine residues to the site created (the 5’ terminal),
which is then followed by the addition of methyl groups by the enzymes
methyltransferases.

8. TAILING:
• Tailing, also known as polyadenylation, is the process of cleavage of the 3’ end and
addition of adenylate residues to the same end of the pre-mRNA.
• A conserved sequence 5’-AAUAAA-3′ is present near the 3’ end of the primary
transcript that is a polyadenylation signal sequence.
• The endonucleolytic cleavage takes place 10-30 base pairs down this signal
sequence, leaving the AAUAAA sequence in the transcript.
• A GU rich region is also present downstream this signal sequence that helps in
cleavage and polyadenylation.
• The enzyme poly-A polymerase then adds adenine nucleotides (200-250 in number)
to the cleaved pre-mRNA. This addition of adenine residues is called poly-A tailing or
polyadenylation.

10. SPLICING:
• There are many non coding sequences present in the primary transcript that can
intervene in the process of translation.
• The removal of these non-coding sequences (known as introns) and the reattachment
of the coding sequences into a continuous molecule is the process of splicing.
• The coding sequences are referred to as exons.
• The whole splicing mechanism takes place by recruitment of the spliceosome
machinery.
• This machinery consists of proteins and small nuclear RNAs (snRNA) that recognise
the splicing sites.
• In eukaryotes, the pre-mRNAs are spliced in various combinations to produce different
mature RNAs, this process is referred to as alternative splicing.

12. rRNA PROCESSING:
• In eukaryotes, rRNA processing takes place primarily in the nucleolus,
a specialized region within the nucleus where ribosomal subunits are
assembled. The process involves several steps, including:
1.Transcription: rRNA genes are transcribed by RNA polymerase I,
resulting in a long precursor RNA molecule called pre-rRNA.
2.Cleavage: Pre-rRNA undergoes several cleavage events that generate
the mature rRNA molecules. In eukaryotes, the 45S pre-rRNA precursor
is cleaved into three separate rRNAs: the 18S, 5.8S, and 28S rRNAs.
The cleavage events are catalyzed by a large ribonucleoprotein complex
called the small nucleolar ribonucleoprotein (snoRNP) complex, which
guides the ribonucleases to the specific cleavage sites.

13. 3.Modification: rRNA molecules are heavily modified by enzymes that add
and remove specific chemical groups from the RNA molecule. These
modifications include methylation, pseudouridylation, and others. These
modifications help stabilize the rRNA structure and regulate ribosome
activity.
4.Assembly: The mature rRNA molecules are assembled with ribosomal
proteins to form the two subunits of the ribosome. The small subunit
contains the 18S rRNA and the large subunit contains the 5.8S, 28S, and
5S rRNAs.
• In prokaryotes, rRNA processing occurs in a similar but simpler way
compared to eukaryotes. There is no nucleolus, and the rRNA genes
are transcribed by RNA polymerase alone. The primary transcript

15. tRNA PROCESSING:
1.Transcription: tRNA genes are transcribed by RNA polymerase III,
producing precursor tRNA molecules.
2. Removal of leader and trailer sequences: Non-functional leader and
trailer sequences are removed from precursor tRNAs.
3. Addition of CCA sequence: The 3' end of tRNA molecules is modified
by adding a CCA sequence, which serves as the attachment site for
amino acids.
4. Modification of bases: Bases within the tRNA molecule undergo various
modifications for stability and proper functioning.
5. Splicing (in some cases): Some tRNA precursors contain introns, which
are non-coding regions that need to be removed through splicing.
6. Quality control and proofreading: tRNA molecules undergo quality
control mechanisms to ensure proper folding and functionality.

16. Once processed, mature tRNA molecules participate in protein
synthesis by delivering specific amino acids to the ribosome.

17. • RNA processing is necessary for the production of functional
mRNA molecules that can be efficiently translated into proteins.
• It enables the removal of non-coding regions, generation of
mRNA diversity, addition of important modifications, and
regulation of gene expression, thereby playing a vital role in
shaping the proteome of a cell and maintaining its proper
function.
IMPORTANCE OF RNA PROCESSING:

18. RECENT ADVANCEMENTS

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21. THANK
YOU