FIG. 6.
MVMp permissiveness of rodent and human transformed cells negatively correlates with PKR activity and eIF2α phosphorylation. (A, B) Rodent (MEF, NIH 3T3, PKRo/o, BHK21, and A9) and human transformed (NB324K, U373, and HepG2) cell lines, either mock (−) or MVMp infected, were analyzed for NS1 expression and eIF2α phosphorylation at the indicated time points (hpi) by Western blotting. Panels A and B show results for two representative experiments performed with parallel infections. Membranes were first probed with the anti-phospho eIF2α antibody, then stripped, and subsequently reprobed for total eIF2α accumulation. Note that substantial differences in the levels of total and phosphorylated eIF2α forms were found among the cell lines. Bands were quantified by densitometry, and the ratio between phosphorylated and total eIF2α is shown below. Since the basal level of phosphorylated eIF2α was undetectable in uninfected NIH 3T3 cells, its ratio was set to 0, and an arbitrary value of 1 was assigned to MVMp-infected 3T3 cells at 15 hpi. (C) The levels of PKR protein accumulation in the cell lines, compared to the level for the β-actin (upper) or the eIF2α (lower) housekeeping protein control, are shown. Equal amounts of total protein were probed with the indicated antisera.