Asmid, pM1o, and 400 ng of one of the following expression vectors that encode JCV early genes under the control of the CMV promoter: pCMV:T+/t+/T9+ (lanes 2, 3; all five tumor proteins expressed), pCMV:T+/t2/T9+ (lanes 4, 5; TAg and 3 T9 proteins expressed) or pCMV:T+/t2/T92 (lanes 6, 7; TAg only expressed). The ability of the proteins produced by the second plasmid to drive replication of the or