Two distinct isoforms of human Pan3 exhibit different interaction strengths with PABP. (A) Schematic diagram of two human Pan3 isoforms. (B) RT-PCR and agarose gel electrophoresis analysis of transcripts for the two Pan3 isoforms in the indicated human cell lines. GAPDH mRNA served as a loading control. (C–G) Coimmunoprecipitation (Co-IP) and Western blot analyses showing that HA-Pan3S pulls down more endogenous PABP than HA-Pan3L does, whereas the two Pan3 isoforms pull down similar amounts of endogenous Pan2 (C); myc-PABP exhibits stronger interaction with HA-Pan3S than with HA-Pan3L (D); HA-Pan3L and HA-Pan3S exhibit a similar ability to interact with Pan2-V5 (E,F); and HA-Pan3S and HA-Pan3L have a similar ability to pull down Pan3S-V5 or Pan3L-V5 (G). NIH3T3 cells were transfected with plasmids expressing the indicated epitope-tagged proteins. GAPDH served as a negative control for co-IP. The amount of each “Input” sample loaded onto the gel was 5% (C,E,F), 3% (D), or 15% (G) of the amount of the corresponding lysate used for IP.
