Coupled in vitro transcription-translation reactions were carried out in rabbit reticulocyte lysate using the Promega TNT system according to the manufacturer's instructions. SDS-PAGE followed by coomassie blue staining (to ensure equal loading of samples) and autoradiography was performed according to standard procedures. Blots were imaged using infrared fluorescence of appropriately tagged secondary antibodies and quantified using a LiCOR Odyssey scanner and software. Transcriptional activity of reconstituted RNPs was assessed using pPolI-Flu-ffLuc or pPol-I segment 7 as reporter plasmids. An amount of 50 ng of 3PNP and 20 ng of the reporter were transfected into adherent 293T cells and 48 h later, either luciferase levels from passively lysed cells were measured using a Promega GloMax luminometer or total RNA was extracted and segment 7 mRNA levels determined by reverse-transcriptase primer extension.