Induction of Tax mRNA expression in JPX-9 cells by CdCl₂. JPX-9 cells were treated with 30 μmol/L of CdCl₂ for indicated hours. After incubation, the expression of Tax or β-actin mRNA in the cells was examined by RT-PCR analysis on 1% agarose gel electrophoresis. PCR products for Tax mRNA contain 246-bp fragments, whereas that for β-actin mRNA contains 236-bp fragments. Primer pairs used are 5′-AAACAGCCCTGCAGATACAAAGT-3′ (upper primer) and 5′-ACTGTAGAGCTGAGCCGATAACG-3′ (lower primer) for Tax, and 5′-GACGAGGCCCAGAGCAAGAGAG-3′ (upper primer) and 5′-ACGTACATGGCTGGGGTGTTG-3′ (lower primer) for β-actin. Lane A; CdCl₂-untreated JPX-9 cells. Lane B; JPX-9 cells treated with CdCl₂ for 3 hours. Lane C; JPX-9 cells treated with CdCl₂ for 6 hours. Lane D; JPX-9 cells treated with CdCl₂ for 12 hours. Lane E; Jurkat cells (negative control). Lane F; MT-2 cells (positive control). Lane G; DNA size marker (Hind III digests of λ DNA).