Figure 2.

(A) Induction of creatine kinase (CK) activity by v-P3k. Noninfected CEM or CEM infected with RCAS viruses or PR-A as described in Fig. 1 were kept in MG medium for 2 days and thereafter were maintained in MD medium. Cells were harvested at daily intervals, and CK activity was assayed by using a commercial kit (Sigma). Mean ± SE values were obtained from two (uninfected and PR-A-infected) or three (RCAS and RCAS-v-P3k-infected) independent experiments (two replicate plates per experiment). The CK activity is expressed in μmol of creatine formed per min per mg of total protein extract (U/mg). (B) Induction of muscle-specific proteins by v-P3k. Total proteins were prepared from CEM at day 8 postinfection with RCAS vector (lane 1), RCAS-v-P3k (lane 2), or PR-A (lane 3). Muscle-specific protein levels were analyzed by immunoblot assay by using antibodies specific for MyoD (Santa Cruz Biotechnology), myosin heavy chain (MHC), and desmin (ICN). Actin served as ubiquitously expressed control was detected with an antibody from Sigma. Similar results were obtained in three independent experiments.