DICER-dependent biogenesis of let-7 miRNAs affects human cell response to DNA damage via targeting p21/p27.

Recently, it was reported that knockdown of DICER reduced the ATM-dependent DNA damage response and homologous recombination repair (HRR) via decreasing DICER-generated small RNAs at the damage sites. However, we found that knockdown of DICER dramatically increased cell resistance to camptothecin that induced damage required ATM to facilitate HRR. This phenotype is due to a prolonged G1/S transition via decreasing DICER-dependent biogenesis of miRNA let-7, which increased the p21(Waf1/Cip1)/p27(Kip1) levels and resulted in decreasing the HRR efficiency. These results uncover a novel function of DICER in regulating the cell cycle through miRNA biogenesis, thus affecting cell response to DNA damage.