Abstract
The translational apparatus in cell-free extracts prepared from [mouse fibroblast] L cells infected with reovirus undergoes a time-dependent transition from cap dependence to cap independence. Extracts from uninfected L cells translate capped reovirus mRNA at high efficiency and synthesize the expected 3 size classes of reovirus polypeptides, and the translation is sensitive to m7G(5'')ppp. This same extract translates uncapped mRNA at a much lower efficiency. In contrast, extracts from infected L cells translate uncapped reovirus mRNA at high efficiency and synthesize the correct 3 size classes of polypeptides, and the translation is not sensitive to inhibition by m7G(5'')ppp. Infected cell extracts translate capped mRNA at reduced efficiency (.apprxeq. 25%), the translation is not sensitive to inhibition by m7G(5'')ppp, and the correct 3 size classes of viral polypeptides are not synthesized. These observations may explain how reovirus takes over the host translational apparatus.