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Noble Prize
2006年諾貝爾生醫獎－意外的干擾
http://www.sciscape.org/news_detail.php?news_id=2118
Introduction
Types of RNA
RNA
mRNA
rRNA
Ribosomal RNA
Participate in
protein synthesis
tRNA
Transfer RNA
Interface between
mRNA &
amino acids
ncRNA
Non-coding RNA. Transcribed RNA with a structural,
functional or catalytic role
snRNA
snoRNA
Small nuclear RNA Small nucleolar RNA
-Incl. RNA that
Found in nucleolus,
form part of the
involved in modification
spliceosome
of rRNA
miRNA
Micro RNA
Small RNA involved
regulation of expression
Other
Including large RNA
with roles in
chromotin structure and
imprinting
siRNA
stRNA
Small temporal RNA.
RNA with a role in
developmental timing
Small interfering RNA
Active molecules in
RNA interference
Introduction
What’s miRNA ?
 Primary miRNA (pri-miRNA) :
The life of a miRNA begins as a long miRNA
precursor called pri-miRNA.
 Precursor miRNA (pre-miRNA) :
The miRNA precursor (pre-miRNA) which is about 70
nt and always forms a hairpin structure.
 Mature miRNA (miRNA) :
The mature miRNA is a form of single-stranded RNA
which is typically about 20-25 nt long, and is thought
to regulate the expression of other genes.
miRNA gene
 pri-miRNA (stem-loop
structure) processed by Drosha
 pre-miRNA carried by
Exportin 5 to cytoplasm
 mature miRNA (~22 bp) is
generated by the RNaseIII type
enzyme Dicer
 directed by RISC to the
miRNA target
 mRNA cleavage or impede
its translation into protein
 miRNA genes were found :
1. In the introns of protein-coding genes.
2. In the introns of non-coding RNAs (ncRNAs).
3. Overlap with the exons of ncRNAs.
 miRNA genes can be grouped on the basis of their
genomic locations :
1. Intronic miRNA in protein-coding transcription units.
2. Intronic miRNA in non-coding transcription units.
3. Exonic miRNA in non-coding transcription units.
a : Exonic miRNAs in non-coding transcripts
b : Intronic miRNAs in non-coding transcripts
c : Intronic miRNAs in protein-coding
transcripts
Kim (2005) Nature 376
Inhibition of translation
miRNA, Imperfect match
 Block translation or
mRNA cleavage
siRNA, near-perfect match
 Degrade mRNA