Poliovirus replicase: a soluble enzyme able to initiate copying of poliovirus RNA.

Abstract
The soluble phase of the cytoplasm of poliovirus-infected [human cervical carcinoma HeLa] cells contains an enzymatic activity able to copy RNA without an added primer. This replicase activity was purified 60-fold; it is absent from uninfected cells. Poly(U) polymerase activity copurifies with replicase activity. Although less pure replicase fractions copy a variety of RNA, purer fractions respond better to poliovirus RNA than to other viral RNA. Even the less pure fractions make a specific copy of the added template, as shown by hybridization of the product to its template RNA but not to other RNA. Among homopolymers only poly(A) .cntdot. oligo(U) was copied by the replicase; other primed homopolymer templates were inactive.