Download miRNA

miRNA
Reading:
http://www.ambion.com/techlib/hottopics/rnai/
Lecture notes
Components of the RNAi machinery
are used for other processes.
The first miRNA was discovered in
C. elegans.
lin-14(lf) mutations caused precocious
development.
lin-14(gf) and lin-4 mutations caused
retarded development.
wild type: embryo
preccious: embryo
retarded: embryo
L1
L2
L1
L2
L3
L1
L3
L4
L2
L4
adult
adult
L3…..
lin-14(lf); lin-4(lf) mutants are
precocious.
lin-14 gene (simplified)
loss-of-function
gain-of function
mutations in coding sequences mutations in 3’UTR
lin-4 encodes no protein. Only an RNA.
LIN-14 RNA always present, but protein decreases
through larval development.
lin-4 required for LIN-14 decrease.
lin-4 RNA increases though larval development.
lin-4 RNA potentially could base pair with lin-14 3’ UTR.
LIN-14 protein
lin-4
lin-14
LIN-14
protein in
lin-14(gf)
or lin-4(lf)
lin-4
RNA
Developmental time
LIN-14
protein in
wild type
Model
Used lac-z::lin-14 3’ UTR reporter
transgene to test model
lacZ
lin-14 3’UTR
LacZ decreases through larval development.
lin-4 required for LacZ decrease.
Reduction of Dicer and Risc components results in lin-4
phenotype; also required for LacZ decrease.
miRNA complex
contains Risc proteins
Two Drosophila miRNAs regulate cell
proliferation, apoptosis and fat storage.
~300 estimated miRNAs in C. elegans
~530 estimated miRNAs in humans