Stimulation of thymidine kinase activity in baculovirus infected cells is not due to a virus-coded enzyme

Summary A polyhedrin-positive recombinant autographa californica nuclear polyhedrosis virus (AcNPV) carrying a herpes simplex virus thymidine kinase gene under the control of theSyn XIV promoter, a fusion of synthetic and linker-modified polyhedrin promoters, has been constructed. When this recombinant baculovirus was used to infect a variant ofSpodoptera frugiperda cells deficient in thymidine kinase (TK^–), a high level of TK activity was detected. These results, in conjunction with the demonstration that AcNPV could replicate in TK^– S. frugiperda cells and no TK activity was found throughout infection, imply that the wild type virus-stimulated TK activity observed inS. frugiperda (TK⁺) cells is not contributed by a virus-coded enzyme.