A series of adenovirus type 5 precursor terminal protein (pTP) and DNA polymerase (Ad pol) genes with linker insertion mutations were separately introduced into the vaccinia virus genome under the control of a late genes in vitro and reintroduction of the mutated genes into the Ad genome (17,41). In our studies, a 12-bp synthetic oligonucleotide was inserted into multiple restriction sites 265 on July 6, 2020 by guest http://jvi.asm.org/ Downloaded from supernatant was used as virus stock for all further experiments. Titers of wt and mutant virus stocks were measured by plaque assay on tk-143 cells.