Evidence for editing in the region of the late poly(A) signal. (A) RT-PCR was performed on nuclear RNA isolated 48 h after infection of NIH3T3 cells with wild-type polyomavirus using primers spanning the NdeI sites illustrated in D. These sites lie just upstream of the early poly(A) site and 21 nt downstream from the late poly(A) site. Evidence for editing is observed by resistance to cleavage by NdeI site 21. In this experiment, ∼30% of the RT-PCR product was resistant to NdeI (arrow). (B) Time-course analysis of restriction enzyme resistance of RT-PCR products. RNA tested included that from 12 h post-infection (hpi), 48 hpi and 48 hpi in the presence of aphidicolin to inhibit DNA replication and the early-late switch (Liu and Carmichael 1993). (C) As in A, but RT-PCR was with primers spanning the MboII site shown in D.
