Vaccinia NPH-I, a DExH-box ATPase, is the energy coupling factor for mRNA transcription termination

A termination protein in vaccinia virus that catalyzes ATP hydrolysis and is closely associated with a polymerase-elongation complex has been identified as nucleoside triphosphate phosphohydrolase-I (NPH-I). It is a virus-encoded DNA-dependent ATPase of the DExH-box family. NPH-I has roles in transcription, one with VTF/CE to catalyze release of UUUUUNU-containing nascent RNA from the elongation complex and one alone as a polymerase elongation factor to make readthrough of intrinsic pause sites easier. Vaccinia NPH-I is the energy-coupling factor for eukaryotic transcription termination for mRNA.