The involvement of HDAC activity in transcriptional repression by p68/p72. a) Relief of p68/p72 repression of MLP-CAT transcription by TSA. 1 μg of pcDNA3-GAL4 (pcG4) or GAL4-tagged p68/p72 (p68G4/p72G4) were co-transfected with 9 μg of MLP-CAT and TSA was added 16 hr after transfection, at a final concentration of 300 nM. The values for p68G4 and p72G4 are given relative to the baseline value for the pcG4 vector control, which was set at 1, and represent the average from three experiments. b) Immunoprecipitation/western blotting of myc-tagged p68 and p72 from 293 cells expressing these proteins. Myc-tagged proteins were immunoprecipitated with the anti-myc epitope antibody, 9E10, and western blotted with the same antibody to detect the presence of p68-myc and p72-myc fusion proteins. A myc-tagged pSG5 vector control is included. pSG5, p68 and p72 all refer to myc-tagged versions. H denotes cross reaction with the antibody heavy chain. Molecular weight markers (in kDa) are indicated. Equal amounts of these immunoprecipitated proteins were used in the HDAC activity assay shown in c. c) HDAC activity assay of immunoprecipitated p68 and p72 (see b). HDAC activity in the presence and absence of TSA is shown relative to that of the myc-tagged pSG5 vector control, which was set at 1, and represent the average from three experiments.