Fig 5.

Increased SRp20 is essential for tumor cell growth. (A) Schematic illustration of siRNA target sites in the SRp20 open reading frame (ORF). Arrows represent individual exons and translation directions. Bars above arrows are relative positions of siRNA target sites along with the siRNA names. D-01, D-02, D-03, and D-04 are four different siRNAs in an siRNA pool from Dharmacon. siRNA s12732, which spans the exon 2/exon 3 junction of SRp20 mRNA was from Ambion. (B-E) Knockdown of SRp20 expression affects cancer cell proliferation. SRp20 was knocked down in U2OS cells (an osteosarcoma cell line with wild-type p53 and pRb) and HeLa cells (an HPV18⁺ cervical cancer cell line) by the Dharmacon siRNAs (40 nM, B-C) or Ambion siRNA s12732 (10 nM, D-E). Insets show SRp20 knockdown efficiency in monolayer cultures by Western blot on day 2 (D2, B-C) and day 4 (D4, B-E) after RNAi. Arrows indicate the days the cells received siRNA treatments. Below the line graphs of B and C are crystal violet staining of the corresponding cells after RNAi. NS, nonspecific siRNA. (F) SRp20 knockdown-mediated cell apoptosis. Poly(ADP-ribose) polymerase (PARP) cleavage was analyzed by Western blot as an apoptotic biomarker ⁶¹ in U2OS cells after SRp20 knockdown with the indicated siRNAs in A.