ADP-ribosyltransferase that efficiently ADP-ribosylates one of the two alpha subunits of host RNA polymerase RPOA on an arginine located in the C-terminal region. ADP-ribosylation of RPOA alpha subunit enhances the transcription of viral early genes. Also ribosylates RPOA subunits beta, beta' and sigma 70 and performs an autoribosylation reaction. L-arginyl-[protein] + NAD(+) = H(+) + N(omega)-(ADP-D-ribosyl)-L-arginyl-[protein] + nicotinamide About 25-50 copies per virion. This protein is injected into the bacterial cell along with the viral DNA. Belongs to the Tevenvirinae NAD(+)--arginine ADP-ribosyltransferase family.