To find if co-expression of nonfunctional NSs is able to attenuate PKR degradation function of MP-12 NSs, VeroE6 cells were infected with MP-12 and then co-infected with rMP12-C13type or one of the NSs truncation mutants using an moi of 3. Cells were collected at 16 hpi and Western blot was used to measure abundance of PKR and RVFV NSs. However, it was found that levels of MP-12 NSs accumulation were not identical to those expressing truncated NSs (Fig. S3) . Only cells co-infected with NSD6-30 and NSD56-80 allowed an efficient accumulation of MP-12 NSs. As a result, PKR was abundantly detected in cells infected with MP-12 and NSs mutants.