Northern analysis of mRNA expression for JCV T antigen in PMA-treated KG-1 cells transfected with the plasmids containing NF-1 class A, B, C, and D, respectively. (The NF-1 plasmids pCHAmNF1-A1.1, pCHAmNF1-B2, pCHAmNF1-C2, and pCHAmNF1-X2 were described in Materials and Methods.) Specific radiolabeled probes for JCV and GAPDH were used to hybridize each RNA sample. The arrow on the right indicates the mRNA species for JCV T antigen.