Human cytomegalovirus induces DNA-dependent RNA polymerases in human diploid cells.

Endogenous RNA polymerase activity was enhanced in human embryonic cells infected with human cytomegalovirus (HCMV) as determined by the incorporation of [³H]UTP into nuclear monolayers. The increase in activity was first detected about 18 hr postinfection, and reached a level 3-fold higher by 48 hr. This kinetics of enhancement coincided with the kinetics of [³H]uridine incorporation into RNA in the infected, intact cells. The treatment of HCMV-infected cells with either cycloheximide or actinomycin D during the first 6 hr of infection practically abolished the subsequent enhancement of endogenous RNA polymerase activity, suggesting a key role of a HCMV-induced early protein(s) in the stimulation of endogenous RNA polymerase activity. Multiple forms of cellular RNA polymerases from HCMV- or mock-infected cells were separated by DEAE-Sephadex chromatography and assayed using calf thymus DNA as a template. In HCMV-infected cells, there was a marked increase in the activity of three major classes of RNA polymerases; the activity corresponding to RNA polymerase II increased 16-fold and those corresponding to polymerases I and III 6- and 3-fold, respectively.