Structure and function of micro RNA

1. SUBMITTED BY- LAVI BHARTI
SUBMITTED TO- DR.ARUN PRATAP
ZOM- 704
GD/ SEMINAR-MICRO RNA

2. INTRODUCTION
 Micro RNA (mi RNA) are small, single-stranded, non-coding
RNA molecules containing 21 to 23 nucleotides.
 Found in plants, animals and some viruses.
 miRNAs are involved in RNA silencing and post-
transcriptional regulation of gene expression

3. HISTORY
 First mi RNA was discovered in 1993 by a group led by
ambros.
 However, mi RNAs were not recognized as a distinct
class of biological regulators until the early 2000
 In 2000 and 2nd small RNA was characterize.
 The first human diseases associated with deregulation
of mi RNA was chronic lymphocytic leukemia

4. LOCATION
On the basis of organism;
1. plants.
2. animal.
3. some virus.
On the basis of cell;
1. Majority mi RNA within the cell.
2. Some are extracellular

5. STRUCTURE OF miRNA
 The structure of mi RNA are formed by the internal
sequence complimentatory in single stranded RNA which
results in the folding of single stranded RNA and leads to
form a stem loop or hair pin like structures.

7. PRE miRNA
• It will become the hairpin loop of the pri-
miRNA (primary miRNA)
• The resulting transcript is capped with a
specially modified nucleotide at the 5’
end, polyadenylated with multiple
adenosines (a poly(A) tail).
• Produced from single stranded RNA
• Sequence complementarity
• 100-120 nucleotide long

8. BIOGENESIS
•As many as 40% of miRNA genes may lie in
the introns or even exons of other genes.
•These are usually, though not exclusively,
found in a sense orientation, and thus usually
are regulated together with their host genes

9. STEPS IN BIOGENESIS
• Transcription
• Nuclear Processing
• Nuclear Export
• Cytoplasmic Processing
AND there, it is finally ready!!!!

11. miRNA genes are usually transcribed by RNA
Polymerase II (Pol II)

12. TRANSCRIPTION
 Micro RNA usually transcribe by polymerase II
enzyme.
 Poly 2 attached with the promoter region of the DNA
sequence and transcribe the DNA.
 The resulting transcript is capped with specially
modified nucleotide at the 5’ end and spliced

13. NUCLEAR PROCESSING
 Formation of hairpin loop structure.
 Hairpin is composed of 70 nucleotide each.
 This hairpin is recognized through type of
 protein called D
GDCR 8.
 DGDCR 8 associated with Drosha that cut DNA
making micro processing complex.
 This complex convert the pri-miRNA to pre-miRNA.

14. NUCLEAR EXPORT
 Pre-miRNA transport through a nucleocytoplasmic
transporter protein known as Exportin-5.
 Use GTP as energy.

15. CYTOPLASMIC PROCESSING
 the pre-mi RNA hairpin is cleaved by the RNase III
enzyme Dicer.
 Dicer interact with the 5’ and 3’hairpin and cut the
loop.(means shorting the ds miRNA).
 AGO2 bind with the ds miRNA and unwanted and convert to
single stranded guide miRNA.
 Guide strand is complementary to the target mRNAand
 inactivate the mRNAtrough two process.
1-Cut on mRNA .
2-Inhibition.

16. RNA induce silencing
complex (RISC)
• The Argonaute protein consists of 2
domains:
1. PIWI domain: break down single
stranded RNA
2. PAZ domain: Attach and bind with
a single stranded RNA
• PAZ will bind with one stand only
which will be called the guide strand
and the strand that will leave is the
passenger strand.

17. RISC
• RNA induced scilencing compex
• The RISC consists of:
1. Slicer
2.Argonaute protein (found in all
types of RISC)
3. TRNC6
• The miRNA: miRNA* duplex is
loaded on the RISC complex

19. FINALLY

21. CONT...
 Silencing may occur either through degradation or
preventing mRNA from being translated.
 The relation of miRNA and its target is base on
negative regulation of target mRNA.
 Here common scenario is use i-e feed- forward loop.

23. REFERENCES
 https://www.slideshare.net/ibadali14/microrna-and-thier-role-
in-gene-regulation
 https://www.slideshare.net/MohamedElasalyPTCKTP/micro-
rna-biogenesis-function-and-nomenclature
 https://en.m.wikipedia.org/wiki/MicroRNA

24. THANK YOU…