FIG. 3.

3′-dCTP blocks negative-strand RNA elongation immediately after copying the poly(A) tail into VPg-linked poly(U). Denaturing 7 M urea-20% polyacrylamide gel of negative-strand RNA products from 40-μl reaction mixtures containing 150 μCi of [α-³²P]UTP (final concentration of 4.7 μM UTP; 800 Ci/mmol UTP) without (lanes 2 to 4) and with (lanes 5 to 7) 3′-dCTP. RNA products were digested with 30 U/μl RNase T1 only (lanes 2, 4, 5, and 7) or RNase T1 and 200 μg/ml proteinase K (lanes 3 and 6). RNA2 template labeled with [α-³²P]UTP digested with RNase T1 is in lane 1. Sizes of positive-strand RNA template fragments, negative-strand RNA fragments, and poly(U) size with or without VPg are labeled. GuHCl, guanidine HCl.