Tax-induced proteolytic degradation of IκB. JPX-9 cells were incubated with CdCl₂ (20 μmol/L) for the indicated time periods and then collected for preparation of either total cellular RNA or whole-cell extracts. (A) Total RNA isolated from either nontreated or CdCl₂-treated JPX-9 cells was subjected to Northern blot analysis with Tax, IκB, and GAPDH probes. (B) Whole-cell extracts isolated from CdCl₂-treated JPX-9 cells were subjected to Western blotting using anti-IκB antibody.