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Fig. 3
Small molecules discovered by cell-based screens, which modulate
miRNA activity. While the mechanism of action has not been elucidated, many
are thought to function via regulation of pri-miRNA transcription
research must still be accomplished to elucidate their mechanism of
action and characterize their degree of specifi city.
Using a similar dual-luciferase assay, studies in the Bhadra lab
identifi ed a group of aza-fl avanones capable of inhibiting
Drosophila
miR-14 and its human homolog miR-4644 [
42
]. After screening
nine compounds,
5
and
6
resulted in an ~400 % increase in lucifer-
ase signal (Fig.
3
), which was confi rmed by qRT-PCR assays and
cell cytotoxicity assays (albeit only in a twofold differential toxicity
relative to healthy cells). The activity of the two compounds was
then translated to a
Drosophila
system and used to increase reporter
GFP expression in larval wing discs carrying a sensor system which
harbored miR-14-binding sites in the 3
UTR of a GFP gene
(Fig.
4
). However, the amount of EGFP expression assessed by gel
electrophoresis did not appear to be substantially increased by the
presence of the compounds.
Interestingly, all three studies afforded compounds that ulti-
mately altered pri-miRNA levels (most likely by transcriptional
repression) despite being screened against the entire miRNA
biogenesis pathway. Further studies are required to ascertain the
′
