Analysis of the replication efficiency of JCV WT and its Pt mutant in agnoprotein positive cells. (A) SVG-A cells were stably transfected with an agnoprotein expression plasmid and clones selected as described in Materials and Methods. Cells expressing agnoprotein or the control cells (stably transfected with empty vector) were transfected with either JCV Mad-1 WT or its Pt mutant genome as indicated. Low molecular weight DNA was isolated and analyzed by Dpn I-Southern blot analysis as described in Figure. 5A. In lane 1, JCV Mad-1 WT genome (2 ng) digested with BamH I was loaded as a positive control (+ Cont.). (B) Western blot analysis of the stable expression of agnoprotein in SVG-A cells. In lane 1, whole cell extracts prepared from the SVG-A cells stably transfected with empty vector were loaded as negative control (- Cont.). In lane 2, whole cell extract prepared from an agnoprotein positive clone was loaded.