A sensitive non-radioactive northern blot method to detect miRNAs was performed as above (42 (link)). The northern blot analysis was carried out using microRNA Detection Probes with DIG-labeling (Exiqon) and a chemiluminescent reaction by enzyme-immunoassay. Firstly, equal amount of in vitro processing RNA substrate was dissolved in TBE-Urea Sample Buffer (Invitrogen), and heated at 95°C for 5 min then rapidly cooled on ice. The RNA was then loaded onto a denaturing 15% polyacrylmide–7.5 M urea gel and transferred electrophoretically to Hybond Nmembranes (Amersham Pharmacia Biotech). The membrane was dried at 80°C for 10 min and then pre-hybridized in 10 ml of pre-heated DIG Easy Hyb (Roche) at 45°C for 1 h. The membrane was hybridized overnight with the hsa-miR-21 DIG labeled LNA-DNA probe (Exiqon) at the concentration of 5 pmol/ml in hybridization oven at 53°C. After hybridization and washing, the membrane was detected with DIG Luminescent Detection Kit (Roche) according to the manufacturer's instructions. Lastly, the membrane was exposed to Amersham Hyperfilm ECL (GE Healthcare Life Sciences, Piscataway, NJ). The bar graphs corresponding to the northern blots were generated through densitometric analysis with ImageJ software.