Inhibits host transcriptional machinery, by producing modifications to the phosphorylation state of the C-terminal domain (CTD) of RNA polymerase II. Inhibits phosphorylation at serine 2 in the heptapeptide repeat (YSPTSPS) of the CTD of RNA polymerase II, suggesting that the elongation step of transcription and/or 3'-end processing is prevented. Inhibition of host transcription machinery leads to shut off of host cell protein synthesis and inhibition of the host innate immune response. NSs also seems to be involved in the nuclear relocalization of host PABP1 (By similarity). Belongs to the orthobunyaviruses NS-S protein family.