RNA-dependent RNA polymerase, which is responsible for the replication and transcription of the viral RNA genome using antigenomic RNA as an intermediate. During transcription, synthesizes subgenomic RNAs and assures their capping by a cap-snatching mechanism, which involves the endonuclease activity cleaving the host capped pre-mRNAs. These short capped RNAs are then used as primers for viral transcription. The 3'-end of subgenomic mRNAs molecules are heterogeneous and not polyadenylated. The replicase function is to direct synthesis of antigenomic and genomic RNA which are encapsidated and non capped. As a consequence of the use of the same enzyme for both transcription and replication, these mechanisms need to be well coordinated. These processes may be regulated by proteins N and Z in a dose-dependent manner. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) For endonuclease activity. Binds 2 Mn(2+) ions in the active site. The divalent metal ions are crucial for catalytic activity. For polymerase activity. Homomultimer; the oligomeric structure is essential for the polymerase activity. Interacts with nucleoprotein N. Interacts with protein Z; this interaction inhibits viral transcription and replication. The N-terminus contains the endonuclease activity (endoN). The central region contains the RdRp activity. Classified as His(-) endonuclease since it does not have a histidine upstream of the active site that coordinates the first cation. His(-) endonucleases display very low activity in vitro, although they are clearly active in vivo. Belongs to the Bunyavirales RNA polymerase family.