Nup358 binds to AGO proteins through its SUMOinteracting motifs and promotes the association of target mRNA with miRISC (2016)
Figure 3

Figure 3. Nup358 interacts with AGO and GW182, and is required for coupling miRISC with target mRNAs

A. HeLa cells were transfected with control, Dicer or Nup358 specific siRNAs, as indicated. Upper panel, total RNA was isolated and analyzed by northern blotting for let-7a using radio-labeled probe. Ethidium bromide (EtBr) stained gel indicates equal loading of RNA samples. Bottom panel, total RNA was isolated from control, Dicer or Nup358 siRNA treated cells and was reverse-transcribed using TaqMan microRNA reverse transcription kit. The levels of let-7a were quantified by qPCR following manufacturer’s instructions. Graph represents the relative levels of miRNAs as compared to U6 RNA control. The values were further normalized to let-7a levels in control siRNA knockdown condition. Data are presented as mean SD (n = 3).

B. HeLa cells were transfected with indicated siRNAs, followed by RL-3xBulge construct. Immunoprecipitation (IP) was performed with control mouse IgG (IgG IP) or anti-AGO2 antibody (AGO2 IP) using lysates prepared from these cells. Total RNA was isolated from control and AGO2 immunoprecipitates and the levels of AGO2 associated let-7a (top left panel) and miR-17 (top right panel) were quantified by q-PCR. Graph represents the extent of miRNAs associated with AGO2 as compared to U6 RNA (as a negative control) with AGO2. Bottom left panel; RNA isolated from IgG control or AGO2 immunoprecipitate samples was reverse-transcribed using oligo(dT) primer. RL-3xBulge mRNA association with AGO2 was quantified by q-PCR and normalized to the level of GAPDH mRNA associated with AGO2. Bottom right panel; AGO2 immunoprecipitates were analyzed by western blotting using AGO2 specific antibody. Vinculin was used as loading control. Data are presented as mean SD (n = 3).

C. HeLa cells were transfected with control (siControl) or Nup358 specific siRNA (siNup358) for 96 h. Cells were lysed and subjected to immunoprecipitation with control IgG (IgG IP) or anti-AGO2 (AGO2 IP). Total RNA was extracted from initial lysate and IP samples and analyzed by q-PCR for validated miRNA targets, Serbp1 and Dnajb11. GAPDH was considered as negative control. Data expressed as the relative amount of target mRNA associated with AGO2 as compared to GAPDH mRNA. Western blots indicate the extent of Nup358 depletion and AGO2 immunoprecipitation in siControl and siNup358 samples. Vinculin was used as loading control. Data are presented as mean SD (n = 3), P‐value was calculated using Student's t‐test.

D. HeLa cells were treated with indicated siRNAs for 96 h. Cells were lysed and analyzed for extent of Nup358 depletion and for the levels of validated miRNA targets, Ras and c-Myc by western analysis. Vinculin was used as loading control.

E. HeLa cells were lysed and immunoprecipitation was performed with control (IgG-IP) or Nup358 (Nup358-IP, left panel) or AGO2 (AGO2-IP, right panel) using specific antibodies. The immunoprecipitates were washed with a buffer containing (+) or not containing (-) RNAse A and probed for the presence of indicated proteins by western blotting.

F. HeLa cells were transfected with RL-3xBulge construct and immunoprecipitation was performed using control (IgG-IP) or Nup358 (Nup38-IP) antibodies. Total RNA was isolated from the immunoprecipitates and analyzed for let-7a miRNA (left panel), RL-3xBulge mRNA and the endogenous miRNA target Dnajb11 using q-PCR (right panel). Fold enrichment in Nup358-IP as compared to IgG-control was calculated and the data are presented as mean SD (n = 3), P‐value was obtained using Student's t‐test.