Measles virus (MV) C protein has been known a multifunctional protein involved in anti-IFN response, viral RNA synthesis, and so on. Recent studies have clarified that double-stranded RNA (dsRNA) is derived from viral genomic RNA (vRNA), and the amount of dsRNA was increased in an MV lacking C protein (MV(C-))-infected cells, suggesting that C protein blocks viral RNA synthesis. However, detailed roles of C protein in viral RNA synthesis remain unknown. Here, we have confirmed through time course experiments using Vero/hSLAM cells that as reported previously, the amount of mRNA is increased in MV(C-)-infected cells at 36 h post infection (hpi). In contrast, we found that the transcription level is lower in MV(C-)-infected cells than wild-type MV-infected cells in early phases of infection. Immunoprecipitation assays were performed to find an interactor(s) of C protein, revealed that C protein interacts with N protein in the absence of vRNA and P protein. RNA immunoprecipitation (RIP) assays showed that the interaction between N protein and vRNA was increased in MV(C-)-infected cells. These results suggest that in early phases of infection C protein facilitates viral transcription to control the formation of nascent nucleocapsid composed of N protein and vRNA. (C) 2015 Elsevier Inc. All rights reserved.