1. Noble Prize

2. 2006年諾貝爾生醫獎－意外的干擾

3. Introduction
Types of RNA

4. 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 nt long, and is thought to regulate the expression of other genes.

5. 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

6. 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.

7. Kim (2005) Nature 376 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

8. Inhibition of translation
The enzyme Dicer generates microRNAs that bind imperfectly to target mRNAs, blocking protein production (left); in RNAi, the RNAs made by Dicer bind tightly to mRNAs, targeting them for doom.
Nature © Macmillan Publishers Ltd 2002 Registered No England.
miRNA, Imperfect match
 Block translation or
mRNA cleavage
siRNA, near-perfect match
 Degrade mRNA