FIG. 4.

FMDV RNA synthesis in infected LF-BK tTA and NTPDase6-expressing cell clones. Equal numbers of cells were infected with FMDV O/UK/2001 and at the times postinfection indicated in the figure; total RNA was extracted and quantified by use of a spectrophotometer. Equal amounts of RNA were loaded in each lane lane, and Northern blotting was performed by using the ³²P-labeled 3D antisense RNA probe as described in Materials and Methods. Infection of cell clone 8 and clone 30 at an MOI of 0.1 in the absence of doxycycline (A) and infection of cell clone 30 at an MOI of 0.1 in the absence or presence of 2 μg/ml doxycycline (B). The lower panels show corresponding levels of ß-actin mRNA as a control.