In vitro translation in reovirus- and poliovirus-infected cell extracts. Effects of anti-cap binding protein monoclonal antibody.

Monoclonal antibodies directed against rabbit reticulocyte cap binding proteins were used as probes to study cap-dependent translation initiation in mock-infected and virus (poliovirus or reovirus)-infected cells. The antibodies inhibited capped mRNA translation, but did not have any effect on the translation of naturally uncapped mRNAs in uninfected cell-free extracts prepared from either L-cells or HeLa cells. Cell-free extracts prepared from either reovirus-infected L-cells or poliovirus-infected HeLa cells did not support capped mRNA translation. However, translation of naturally uncapped mRNAs in the latter extracts was comparable to that observed in extracts from uninfected cells. Thus, translation of mRNAs in extracts from either reovirus- or poliovirus-infected cells proceeds most probably via a cap-independent mechanism, since it is not inhibited by antibodies directed against cap binding proteins.