Akter, L.; Kawasaki, J.; Rakib, T. M.; Okura, T.; Kato, F.; Kojima, S.; Oda, K.; Matsumoto, Y.

Paramyxovirus genomes carry bipartite promoters at the 3\' ends of both their genome and antigenome, thereby initiating RNA synthesis, which requires the viral polymerase to recognize two elements: the primary promoter element 1 (PE1) and the secondary promoter element 2 (PE2). We have previously shown that the antigenomic PE2 (agPE2) in many viruses in the Rubulavirinae subfamily is located within the coding region of the viral RNA polymerase L gene. Sosuga virus (SOSV), belonging to the Rubulavirinae subfamily, is highly pathogenic to humans, thus necessitating high-level containment facilities for infectious virus research. The use of a minigenome system permits studies of viral RNA synthesis at lower biosafety levels. Because minigenomes of negative-strand RNA viruses generally comprise only the untranslated regions, agPE2 within the L coding region--such as those found in Rubulavirinae like SOSV--are typically omitted. However, generating an SOSV minigenome that retains agPE2 led to a pronounced increase in activity, enabling a detailed examination of the role of agPE2 in SOSV replication. In many Rubulavirinae, the agPE2 not only acts as a promoter but also encodes part of the L protein, resulting in a distinct motif at the C-terminus of the L protein. We have further shown that this motif is preserved even in Rubulavirinae that no longer contain the agPE2 within the L gene.