Fig 4.

PKR activation in infected parental HT1080, dnMEK (HT92-6), and caMEK (HT84-4) cells. To determine the influence of mutant MEK expression on PKR activation, replicate cultures of HT1080, HT92-6, and HT84-4 cells were exposed to 10 PFU per cell of HSV-1(F) wild-type virus (A) or R2621 mutant virus (B). Cells were harvested at 3, 9, and 24 h after infection, and cytoplasmic extracts were prepared as described in Materials and Methods. Electrophoretically separated proteins were immunoblotted with antibodies for total PKR and the phosphorylated form of PKR (on threonine 446) (p-PKR). GAPDH was used as a loading control. The fold induction of the phosphorylated form of PKR was determined using the TINA program to measure the intensity of the band normalized to GAPDH.