Expression of a functional influenza viral cap-recognizing protein by using a bovine papilloma virus vector.

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Abstract
The gene for the influenza viral PB2 protein, which recognizes and binds the 5''-terminal cap 1 structures (m7GpppNm) on eukaryotic mRNA species, was inserted into a bovine papilloma virus vector under the control of a mouse metallothionein I (MT-I) promoter. After transfection of this vector into mouse NIH 3T3 cells, a cell line, cPB2, was obtained that produces PB2-specific mRNA and authentic PB2 protein. Induction of the MT-I promoter with CdCl2 causes an .apprx. 10-fold increase in PB2 mRNA and protein levels. The expressed PB2 protein is functional, as it relieves the block in viral mRNA synthesis exhibited by a temperature-sensitive viral mutant containing a cap-binding defect in the PB2 protein. This demonstrates complementation of a function of a negative-strand RNA virus by a gene product expressed in a cell line from recombinant DNA.