IJMS, Vol. 15, Pages 15552-15570: Structures and Functions of Q? Replicase: Translation Factors beyond Protein Synthesis (International Journal of Molecular Sciences)

Q? replicase is a unique RNA polymerase complex, comprising Q? virus-encoded RNA-dependent RNA polymerase (the catalytic ?-subunit) and three host-derived factors: translational elongation factor (EF) -Tu, EF-Ts and ribosomal protein S1. For almost fifty years, since the isolation of Q? replicase, there have been several unsolved, important questions about the mechanism of RNA polymerization by Q? replicase. Especially, the detailed functions of the host factors, EF-Tu, EF-Ts, and S1, in Q? replicase, which are all essential in the Escherichia coli (E. coli) host for protein synthesis, had remained enigmatic, due to the absence of structural information about Q? replicase. In the last five years, the crystal structures of the core Q? replicase, consisting of the ?-subunit, EF-Tu and Ts, and those of the core Q? replicase representing RNA polymerization, have been reported. Recently, the structure of Q? replicase comprising the ?-subunit, EF-Tu, EF-Ts and the N-terminal half of S1, which is capable of initiating Q? RNA replication, has also been reported. In this review, based on the structures of Q? replicase, we describe our current understanding of the alternative functions of the host translational elongation factors and ribosomal protein S1 in Q? replicase as replication factors, beyond their established functions in protein synthesis.