FIG. 5.

PRP4 phosphorylation observed in kinase assays is unique to SF2 protein. 293T cells were transfected with either empty vector (pCDNA3.1V5HisA) or vector containing full-length PRP4 fused to a V5 epitope tag (pCDNA3.1V5PRP4FL). Cells were lysed and protein was immunoprecipitated as described in Materials and Methods. Empty vector protein (lanes 1, 3, and 5) and PRP4 protein (lanes 2, 4, and 6) were used in a kinase assay as phosphorylating agents. GST fusion proteins were used as targets of phosphorylation: GST alone (lanes 1 and 2), GST fused to HIV-2 Gag (lanes 3 and 4), and GST fused to SF2 protein (lanes 5 and 6).