Recombinant Rotavirus A RNA-directed RNA polymerase, partial

RNA-directed RNA polymerase that is involved in both transcription and genome replication. Together with VP3 capping enzyme, forms an enzyme complex positioned near the channels situated at each of the five-fold vertices of the core. Following infection, the outermost layer of the virus is lost, leaving a double-layered particle (DLP) made up of the core and VP6 shell. VP1 then catalyzes the transcription of fully conservative plus-strand genomic RNAs that are extruded through the DLP's channels into the cytoplasm where they function as mRNAs for translation of viral proteins. One copy of each of the viral (+)RNAs is also recruited during core assembly, together with newly synthesized polymerase complexes and VP2. The polymerase of these novo-formed particles catalyzes the synthesis of complementary minus-strands leading to dsRNA formation. To do so, the polymerase specifically recognizes and binds 4 bases 5'-UGUG-3' in the conserved 3'-sequence of plus-strand RNA templates. VP2 presumably activates the autoinhibited VP1-RNA complex to coordinate packaging and genome replication. Once dsRNA synthesis is complete, the polymerase switches to the transcriptional mode, thus providing secondary transcription.