Journal: Nucleic Acids Research
Article Title: Phosphorylation of the alternative mRNA splicing factor 45 (SPF45) by Clk1 regulates its splice site utilization, cell migration and invasion
doi: 10.1093/nar/gkt170
Figure Lengend Snippet: Clk1 enhances SPF45-induced exon 6 exclusion from Fas mRNA. ( A ) SKOV3 cells were transfected with siRNA against SPF45 (siSPF45) or scrambled control siRNA (scr) for 72 h, and RNA was isolated. Endogenous Fas spliced isoforms were analysed by RT-PCR using primers flanking exon 6. PCR products representing mRNA including exon 6 [Fas (L)] and excluding exon 6 [Fas (S)] are shown and are quantified in the graph, with the ratio Fas (S) to Fas (L) set to one in the control siRNA group. The resuslts are from three independent experiments performed in duplicate and were statistically significant. ( B ) Parallel cultures to those in (A) were lysed for western blotting using antibodies to SPF45 and actin. ( C ) Cell lysates from the indicated cell lines were immunoblotted for SPF45 using a polyclonal antibody to recombinant His-SPF45. COS-1 cells transfected with untagged SPF45 (COS-1, +con) and OV2008 cells expressing control or SPF45-specific shRNA served as positive controls. The SPF45 band (SPF45) and an SPF45 degradation product (degr.) in the positive control lane are labelled. ( D ) COS-1 cells were cotransfected with Myc-SPF45 (0.6 μg) and Clk1 (0.8 μg) and endogenous Fas spliced products were analysed by RT-PCR 24 h after transfection. A representative gel is shown. The means and SE for the relative ratio of exon 6 exclusion from three experiments done in duplicate are shown under the gel images. ( E ) Schematic of the Δ Fas minigene splicing reporter used in transfection assays and the different mRNA isoforms derived from it, representing inclusion or exclusion of exon 6. ( F ) SPF45 expression induced exon 6 exclusion in a dose-dependent manner. COS-1 cells were co-transfected with Δ Fas and increasing amounts of Myc-SPF45. Total RNA was extracted at 24 h and analysed by RT-PCR using Δ Fas -specific primers. A representaive gel from at least three independent experiments is shown, and the ratio of the lower band to the upper band is shown below the gel. The lower panel represents a western blot of Myc-SPF45 and actin protein expression from one experiment. ( G ) Clk1 overexpression promotes SPF45 alternative splicing activity. COS-1 cells were cotransfected with Δ Fas (0.3 μg), Myc-SPF45 (0.6 μg) and Clk1 (0.8 μg), and spliced products were analysed by RT-PCR 24 h after transfection. A representative gel is shown. The means and SE for the relative ratios of exon 6 exclusion are shown under the gel images. Results were derived from three independent experiments done in duplicate. Statistical significance ( P < 0.01) is indicated in the graph. ( H ) Clk1 overexpression enhanced SPF45 protein levels. Protein lysates were prepared from cells transfected as in (G) and were subjected to western blotting using antibodies to Myc, Clk1 and actin.
Article Snippet: Quantitative real-time PCR was carried out using either Taqman Gene Expression Assays: Hs00269734_m1 for Clk1 and Hs99999901_sl for the housekeeping gene of 18S RNA on a 7300 Real-Time PCR System (Applied Biosystems) or Bio-Rad’s SsoAdvancedTM SYBR® Green Supermix on an Eppendorf (Hauppage, NY) Mastercycler Realplex 2.
Techniques: Transfection, Control, Isolation, Reverse Transcription Polymerase Chain Reaction, Western Blot, Recombinant, Expressing, shRNA, Positive Control, Derivative Assay, Over Expression, Alternative Splicing, Activity Assay