a, PASMCs were transfected with control siRNA (Control-siRNA) or a mixture of siRNAs for SMAD1 and SMAD5 (SMAD-siRNA). After BMP4 treatment (2 h), the expression of pri-miR-21, pre-miR-21 and mature miR-21 was compared (top panel). As controls, expression of ID3, SMAD1, SMAD5 and SMA is shown (bottom panel). NS, not significant (P > 0.05). b, PASMCs were transfected with control siRNA (Control-siRNA) or siRNAs for p68 (p68-siRNA). Expression of pri-miR-21, pre-miR-21 and mature miR-21 was examined after BMP4 treatment (2 h) (*P < 0.05; n = 3). c, Nuclear extracts prepared from PASMCs treated with BMP4 (2 h) and subjected to immunoprecipitation with anti-p68, anti-DROSHA antibody, or non-specific IgG (control), followed by immunostaining with anti-SMAD1/5, anti-p68 or anti-DROSHA antibody. Nuclear extracts were immunostained with anti-lamin A/C antibody (control). IB, immunoblot; error bars represent s.e.m.