Abstract
Messenger RNA (mRNA) with sequences of polyriboadenylic acid (poly A) has been isolated from the cytoplasm of vaccinia virus-infected cells after a short pulse label with radioactive uridine. No labelled RNA containing poly A was isolated from mock-infected cells under the same conditions. mRNA synthesized at various times during the replicative cycle was examined by polyacrylamide gel electrophoresis and compared with the mRNA synthesized in the presence of inhibitors of protein and DNA synthesis. No difference was detected between class 1 and class 2 early mRNA species although late RNA species were on average considerably larger than the early species.