On cloning ectromelia viral DNA fragments in Escherichia coli minicell
s, the expression of additional proteins was revealed; the transcripti
on of their mRNA appeared to be initiated within the cloned fragments.
From experiments with the lacZ gene inserted into the HindIII site of
pBR322 together with ectromelia or vaccinia virus DNA fragments, it i
s concluded that AT-rich sequences of orthopoxviruses can function as
promoters for bacterial RNA polymerase.