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. 2006 Dec 7;35(2):e10. doi: 10.1093/nar/gkl1045

Figure 5.

Figure 5

Pol I-dependent shRNA induces silencing of endogenous gene expression. (A) Western blot using 20 μg of protein extracts from electroporated IDG3.2 ES cells. A total of 50 μg of each of the plasmids pU6-shErk2, pE3SP-shErk2, pE3SP-shCon and pE3SP-MCS were transfected. The western blot shows the expected double-band for Erk1 (upper band) and Erk2 (lower band). Erk2 is specifically down-regulated in the samples from the transfected Pol III-driven (first lane) and Pol I-driven (second lane) RNAi expression vectors. Erk1 expression remains unaffected by the introduced RNAi and control vectors (lanes 3 and 4). (B) Quantification of band intensities in western blot shown in (A). The numerical values from the band intensities of the Erk2 signals were normalized to those of Erk1 (mean ± SD; Student's t-test: ***P < 0.001, **P < 0.01). There is a significant and strong down-regulation of Erk2 by shRNAs either derived from Pol III (first column) or Pol I promoters (second column). Unrelated shRNAs (third column) and empty expression vectors (fourth column) show no statistical effect on the expression of Erk2.