Figure 5.

Mutations introduced in the CRE of Theiler’s virus. The stem and loop structure of virus DA1 is presented as predicted by Palmenberg and Sgro (27). The conserved 9-nt sequence is outlined. Mutations were introduced by site-directed mutagenesis with the indicated oligonucleotides in a cloned subfragment containing the CRE. The mutated fragment was subsequently reintroduced into pEL8, a replicon containing a 374-nt fragment (amplified with primers TM57-TM86) encompassing the CRE. pEL8 is identical to pTM607 (See Fig. 1) except that it contains 12 additional viral nucleotides at the 3′ end of the CRE fragment. + and − indicate the replication abilities measured by dot blot after transfection of the replicon RNA in BHK-21 cells.