The NS1 proteins of some influenza strains induce cellular shutoff by blocking the maturation of RNA polymerase II transcripts and the nuclear export of host mRNAs, a mechanism mediated by its ability to bind to the cleavage and polyadenylation specific factor 30 (CPSF30) host protein [19,41,48,49], and to the poly(A)-binding protein II (PABII) [18]. This evidence concerns the gene CPSF4 and influenza.