Because GRB2 binding to hPIV3-C and hPIV3-C 90-195 were essentially equivalent in co-affinity purification experiments, we hypothesized that the N-terminal region of hPIV3-C was required for its proper subcellular localization. Thus, hPIV3-C, hPIV3-C 90-195 and hPIV3-C 1-89 were expressed in fusion downstream of the red fluorescent protein Cherry. As shown in Figure 8C , Cherry alone or fused to hPIV3-C 90-195 localized both in the nucleus and the cytoplasm of transfected cells. In contrast, full-length hPIV3-C essentially accumulated at the cellular membrane whereas hPIV3-C 1-89 was in the nucleus. Although we have no explanation for this unexpected localization of hPIV3-C 1-89 , these observations show that only full-length hPIV3-C is able to target the cellular membrane where both IFN-a/b and EGF signaling are triggered.