Differential rna processing dev bio

1. Name: Aysha Tahir
Roll No: 871
Uni Roll No: 023822
Subject: Analysis of development
submitted to: Dr saghir
Class: BS Zoology (6th)
Government college of science whadt road
lahore

2. Differential RNA
Processing

3. RNA Processing
• RNA processing in which a newly made
precursor messenger RNA transcript is
transformed into a mature mRNA.
OR
• The process of modification mainly
through splicing of primary RNA
transcript so as to release functional
RNA molecule from them.

4. Why there is a need of RNA
processing?
To become an active protein:
1. The nuclear RNA must be processed
into by the removal of introns.
2. Translocated from nucleus to
cytoplasm.
3. Post transnationally modified to
become active.
4. Translated by protein synthesis
apparatus.

5. RNA processing in prokaryotes
• In prokaryotes which lack a nucleus can
translate an mRNA as soon as it is
transcribed by RNA polymerase.
• As a consequence there is a little
processing of prokaryotic mRNAs.
• Most bacterial RNA do not undergo
splicing.
"These transcripts are said to be collinear,
with DNA directly encoding"

6. RNA processing in eukaryotes
There are basic three steps in RNA
processing.
1. RNA capping
2. Polyadenylation
3. Splicing of introns

7. • hnRNA stand for heterogeneous nuclear
RNA.
• It refers to the large pre mRNA of various
nucleotide sequence that are made by
RNA polymerase II.
• The primary transcript may range from
500 to 50,000 nucleotide it remain
confined to the nucleus.
• The hnRNA molecule which produce
functional mRNA undergo RNA
processing which include:
What is hnRNA?

8. RNA capping
5’ capping RNA
 After about 30 nucleotide 5’-P is almost
modified
 The phosphate (terminal) is released by
hydrolysis
 The diphosphate 5’ end then attack the alpha
phosphate of GTP to form a very usual 5’-5’
triphosphate linkage this is called
condensation
 The N-7 nitrogen of terminal gene is than
methylated by S-adenosyl methionine form a
cap

9. Steps of capping
Step 1

10. Step 2

11. Step 3

12. Polyadenylation
• Addition of poly A tail
• Poly A tail is added to 3’ end of transcript in
two steps
 Cleavage
The RNA is cut 10 to 30 nucleotide downstream
of a specific sequence in 3 UTR.
 Addition of A’s
100 to 200 A’s added to generate a poly A tail.

14. RNA splicing
this is the controlled excision of large
intervening sequence or introns from the
transcript and rejoining of remaining
fragments called coding sequence or
exon.
Introns Exons
Non-codding sequence mRNA Codding sequence of mRNA

15. snRNA
• Eukaryotic nuclei contain many discreet
small RNA species called nuclear RNA are
rich in base uracil which complex with
specific protein to form snRNPs.
• The most abundant snRNP are involved
in pre mRNA splicing U1, U2, U4, U5 and
U6.
• The snRNPs form a macromolecule
complex called spliceosomes.

16. Mechanism of RNA
splicing/spliceosome
 snRNPs comes together and cut out the
intron and rejoin the end of RNA
 U1 recognize the region of left splicing GU of
the 5’ intron.
 U2 recognize the another sequence called
branch site and attach to it.
 U4, U5, U6 snRNPs form a complex bringing
together both U1 and U2 snRNPs.
 Intron is removed as a lariat-loop of RNA like
a cowboy rope.

20. Alternative splicing
 All noncoding introns are spliced out
of pre mRNA by spliceosomes.
 But not all exons are included in the
final mRNA.
 mRNA can undergo alternative
splicing.