Beta-catenin associates with human parainfluenza virus type 3 ribonucleoprotein complex and activates transcription of viral genome RNA in vitro.

Several studies have indicated that human parainfluenza virus type 3 (HPIV-3) requires polymeric actin for transcription of its genome RNA in vitro and in vivo. In the current study, we have identified beta-catenin, an actin-bound protein, as one of the transcriptional activators for HPIV-3 genome RNA. Beta-catenin was packaged within the purified HPIV-3 virions and was associated with the HPIV-3 ribonucleoproteins (RNP) from infected cells. Moreover, purified beta-catenin interacted with bacterially expressed HPIV-3 nucleocapsid protein (N) and phosphoprotein (P) fused to glutathione S-transferase (GST). Double-labeled immunofluorescent confocal microscopic analysis revealed colocalization of beta-catenin with HPIV-3 RNP at cell periphery in infected cells. The HPIV-3 RNP-associated beta-catenin functioned as a transactivator of HPIV-3 genome, because purified beta-catenin stimulated transcription of viral RNP in an in vitro transcription assay. These results demonstrate that beta-catenin, a multifunctional protein that is involved in cell-cell adhesion and embryogenesis, acts as one of the transcriptional activators of HPIV-3 genome RNA.