Replication of viral RNA. 13. The early product of phage RNA synthesis in vitro.

Studies on the replication of phage RNA, both in vivo and in vitro, led to the suggestion that complementary viral RNA' strands, formed in a first step, serve as tem- plate for the synthesis of viral RNA proper ("plus" strands).This view is in agreement with observations in a number of laboratories (for references, see ref.2).The doubts raised earlier3 regarding the formation of a complex containing "minus" strands during the synthesis of phage RNA in vitro,4 have again been dispelled to some extent by recent work in Spiegelman's laboratory.5Although it was initally assumed6 that the template for plus strand synthesis was a minus strand which formed part of a double helix, further in vitro studies with RNA synthetase7 suggested that the template might in fact occur in a nonhydrogen-bonded form.The present paper shows that formation of Qu RNA by Qua replicase is preceded and accompanied by the synthesis of full-length viral minus strands which are largely RNase sensitive and are therefore not part of a double-stranded helix.A portion of these minus strands occurs in a structure sedimenting around 40S, presumably in association with template plus strands and protein, and is largely con- verted to a double-stranded form during isolation.In agreement with Spiegelman and his collaborators,8 we find that Q, replicase synthesizes net amounts of infectious Qua RNA in the second phase of the reaction.