Optimizing of the loop sequence of si-6-based shRNA in HEK293 cells, as evaluated by RT-PCR: (1) pcPURhU6 si-6 (21 bp)-miR26, (2) si-6 (19 bp) with 9-nt UUCAAGAGA loop, (3) si-6 (21 bp) with 9-nt UUCAAGAGA loop, (4) si-6 (21 bp) with 10-nt CUUCCUGUCA (loop from miRNA23), and (5) si-6 (21 bp) with 19-nt UAGUGAAGCCACAGAUGUA (loop from miRNA30).
