p37 AUF1 relieves saturation of the ARE-mRNA decay pathway. (A) CHO cells were cotransfected with either 1.0 μg of plasmid vector or the Flag-p37 plasmid and 1.5 or 4.5 μg of the β-Gal ARE or GC control reporter plasmids per 107 cells. Total RNA was isolated 24 h posttransfection, and Northern analysis was performed. (B) CHO cells were transfected as in panel A but with a fixed amount of the reporter plasmid (1.5 μg) and an increasing amount of Flag-p37 plasmid DNA (0.1, 0.5, and 1.0 μg), as shown. A representative blot is shown. Autoradiograms were quantified by densitometry, and data were normalized by transfection efficiency, as determined by GFP β-Gal control mRNA with the vector alone set at 100%, as described in the legend to Fig. 1.