Task: Named Entity Recognition
Input (English):  The biological activity of these mutants was tested by determining their capacity to ( i ) reconstitute RNA polymerase activity in vivo by cotransfection with proteins NP , PB1 , and PA and a virion - like RNA encoding the cat gene into vaccinia virus T7 - infected COS - 1 cells and ( ii ) complete with the wild - type PB2 activity .
Output (English): RNA polymerase