DNA-dependent ATPase required for providing the needed energy to achieve the termination of early transcripts. Acts in concert with the RAP94 subunit of the virion RNA polymerase and the capping enzyme/VTF to catalyze release of UUUUUNU-containing nascent RNA from the elongation complex. NPH-I must bind ssDNA in order to exhibit ATPase activity (By similarity). a ribonucleoside 5'-triphosphate + H2O = a ribonucleoside 5'-diphosphate + H(+) + phosphate Monomer. Interacts (via C-terminus) with RAP94 (via N-terminus). Interacts with the cap-specific mRNA (nucleoside-2'-O-)-methyltransferase (By similarity). Virion core enzyme. Belongs to the helicase family. NPH I subfamily.