5-Mercaptopolyuridylic acid (MPU), a potent inhibitor of the reverse transcriptase from avian myeloblastosis virus.

The effects of partially thiolated polyuridylic acid (MPU), partially thiolated polycytidylic acid (MPC), and their unmodified counterparts, poly(U) and poly(C), respectively, on the reverse transcriptase of avian myeloblastosis is virus (AMV) have been determined, using different template-primers. Poly(C) stimulated and MPC inhibited the polymerization reaction catalyzed by the AMV reverse transcriptase in the presence of the natural viral template (endogenous RNA or purified 70S RNA), or with poly(C) . oligo(dG)12-18 but not with poly(A) . oligo(dT)12-18 as the only template-primer present in the purified enzyme system. Both poly(U) and MPU inhibited the reaction in the presence of either of the synthetic or natural templates. Using the purified enzyme with the 70S RNA template, MPU was by far the most potent inhibitor, with I50 = 0.8 microM based on the epsilon (P) value, or I50 less than 3 x 10(-9) M based on the actual, macromolecular weight of the polynucleotide.