MicroRNA-directed transcriptional gene silencing in mammalian cells

MicroRNA-directed transcriptional gene silencing in mammalian cells

submitted by Shang Chu 41864447

In the Beckman Research Institute of the City of Hope, a research team had some interesting findings about miRNAs . The team includes : Daniel H. Kim, Pål Sætrom, Ola Snøve, Jr, and John J. Rossi.
As known, MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional
level in the cytoplasm, but recent findings of the team suggest
additional roles for miRNAs in the nucleus.
To address whether miRNAs might transcriptionally silence gene expression, the team
searched for miRNA target sites proximal to known gene transcription
start sites in the human genome.
One conserved miRNA,miR-320, is encoded within the promoter region of the cell cycle
gene POLR3D in the antisense orientation.
The team provide evidence of a cis-regulatory role for miR-320 in transcriptional silencing of POLR3D expression. miR-320 directs the association of RNA interference (RNAi) protein Argonaute-1 (AGO1), Polycomb group (PcG) component EZH2, and tri-methyl histone H3 lysine 27 (H3K27me3) with the POLR3D promoter.
Their results suggest the existence of an epigenetic mechanism of miRNA-directed transcriptional gene silencing(TGS) in mammalian cells.