Replication of XXXX in vivo requires an interaction between the viral RNA and the TpsiC loop of the @entity3915 primer.

@entity778 @entity410 @entity281 @entity3915 @entity3337
Reverse transcription in @entity778 ( @entity778 ) initiates from the 3' end of a @entity3915 primer, which anneals near the 5' end of the RNA genome. The region around the @entity3337 ( @entity3337 ) forms an elaborate stem structure composed of the U5-inverted repeat (U5-IR) stem, the U5-leader stem, and the association of the tRNA primer with the @entity3337 . There is evidence for an additional interaction between the viral U5 RNA and the T psi C loop of the @entity3915 (U5-T psi C). We now demonstrate that this U5-T psi C interaction is necessary for efficient replication of @entity778 in culture. By randomizing specific biologically relevant regions of the viral RNA, thereby producing a library of mutant viruses, we are able to select, through multiple rounds of @entity281 , those sequences imparting survival @entity410 . Randomizing the U5-T psi C interaction region of the viral RNA results in selection of largely wild-type sequences after five rounds of @entity281 . Also recovered are mutant viruses that maintain their ability to base pair with the T psi C loop of the @entity3915 . To prove this interaction is specific to the tRNA primer, we constructed a second library, in which we altered the @entity3337 to anneal to tRNA(Pro), while simultaneously randomizing the viral RNA U5-T psi C region. After five rounds of @entity281 , the consensus sequence 5'-GPuPuCPy-3' emerged, which is complementary to the 5'-GGTTC-3' sequence found in the T psi C loop of tRNA(Pro). These observations confirm the importance of the U5-T psi C interaction in vivo.
