Figure 6

p21 stabilizes cyclin D prior to infection. 6A: p21 knockdown reduces cyclin D expression. Protein was harvested from Hct116 p21^+/+ and TOV21G cells up to 48 h followed treatment with 60 pmol p21 or scrambled control siRNA. Expression of p21 and cyclin D was assessed by immunoblot. Numbers represent Cyclin D:actin ratio, normalised to Scr-treated controls. 6B: p21 re-expression increases cyclin D. Protein was harvested from 10⁵ ACP-p21 and ACP-GFP cells. Cyclin D and p21 expression was assessed by immunoblot. Numbers represent Cyclin D:Ku70 ratio, normalised to ACP-GFP controls. 6C: Cyclin D knockdown reduces p21 expression and reduces cytotoxicity. Protein was harvested from TOV21G cells 24 h followed treatment with 60 pmol cyclin D or scrambled control siRNA. Expression of p21 and cyclin D was assessed by immunoblot. Numbers represent p21:actin ratio, normalised to Scr-treated controls. TOV21G cells (10⁴ cells/well) were also transfected with 20 pmol cyclin D or scrambled control siRNA in 24 well plates. 24 hours later, they were infected with dl 922-947 (MOI 0, 0.1, 1 and 10). Cell survival was assessed 96 hours later by MTT assay. * p < 0.05. ** p < 0.01.