SUMMARY

Messenger RNA (mRNA) with sequences of polyriboadenylic a id (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 g l electrophoresis and compared with the mRNA synthesized in the presence of inhibitors of protein and DNA synthesis. No difference was detected between 'class I ' and 'class 2 early ' mRNA species although 'late ' RNA species were on average considerably larger than the 'early ' species