2002.09.17

DroshaDrosha

121th Lab meeting121th Lab meeting

석사 2 년

박 은 실

Lin-4, Let-7Lin-4, Let-7

What is RNAi ?

A form of posttranscriptional gene silencing, in which dsRNA induces degradation of the homologous mRNA, mimicking the effect of the reduction, or loss, of gene activity.

Kim VN., Kim VN., J Korean Med SciJ Korean Med Sci . 2003 . 2003

MicroRNAMicroRNA

•Small, Non coding RNAs

•21~25nt long

•Negatively regulate gene expression

•Lin-4, Let-7

•RNAse Ⅲ type enzyme

Kim VN., Kim VN., J Korean Med SciJ Korean Med Sci . 2003 . 2003

stem loops involving the mature miRNAs (red) The miRNAs* (blue)

Examples of Metazoan miRNAsExamples of Metazoan miRNAs Examples of Metazoan miRNAsExamples of Metazoan miRNAs

David P. Bartel. David P. Bartel. cellcell. 2004. 2004

The molecular hallmarks of The molecular hallmarks of lin-4lin-4

The molecular hallmarks of The molecular hallmarks of lin-4lin-4

Lin He and Gregory J.HannLin He and Gregory J.Hannon.on. Nature Nature. 2004. 2004

MiRNAs and SiRNAs — what’s the differeMiRNAs and SiRNAs — what’s the differencence

MiRNAs and SiRNAs — what’s the differeMiRNAs and SiRNAs — what’s the differencence

• terms of their molecular characteristics, biogenesis and effector functions• share a common RNase-III processing enzyme, Dicer, and closely related effector complexes, RISCs, for post-transcriptional repression

•Specific precursor• bind to the target 3′ UTRs through imperfect complementarity at multiplesites

miRNAmiRNA

•sampled more randomly from long dsRNAs•form a perfect duplex with their targets at only one site

siRNAsiRNA

The current model for the biogenesis and post-transcriptional

suppression

The current model for the biogenesis and post-transcriptional

suppression

Two processingTwo processing

First: nascent miRNA(pri-miRNA) → ~70nt precursor (p

re-miRNA)

Second: → 21~25nt mature miRNA

Drosha, Dicer: ds RNA specific endonuclease

Lin He and Gregory J.HannLin He and Gregory J.Hannon.on. Nature Nature. 2004. 2004

The structure and function of the Dicer familyThe structure and function of the Dicer family

Dicer1 and Dicer2Dicer1 and Dicer2•Deficiency in Dicer1 disrupts the processing of pre-miRNAs• loss of Dicer2 affects the production of siRNAs, but not miRNA maturation.

=PAZ domain is only present in Dicer1, but absent in

Dicer2

Argonaute (AGO) proteins include PAZ domain and a piwi domain.

Lin He and Gregory J.Hannon.Lin He and Gregory J.Hannon. Nature Nature. 2004. 2004

Post-transcriptional repression by miRNAsPost-transcriptional repression by miRNAs

• Lin-4 와 lin-14• Let-7(worms), Bantam(flies), miR30 (mam

mal) – negatively regulate• mir-196 = animal 에서 유일하게 그 target

인 Hoxb8 에서 base pairing 이 perfect하여 mRNA 의 destruction 일으킴

• miR-172 = 유일하게 coding 영역에 존재하며 plant 에서 유일하게 repressor로 작용

C. elegans : 116

C. briggsae : 50

D. melanogaster : 78

A. thaliana : 48

Rice : 28

Mouse : 207

Rat : 185

Human : 191

miR-26a and miR-99a miR-26a and miR-99a expression is reduced expression is reduced in human lung cancer in human lung cancer

cell line.cell line.

In vitroIn vitro processing of miRNA by Drosha processing of miRNA by DroshaIn vitroIn vitro processing of miRNA by Drosha processing of miRNA by Drosha

2004.08.05

AGO AGO proteinprotein