Unfolding of the viral cycle 2: replication

Replication is the complete copy of the viral genome. As PPRV is a negative-sense RNA virus, it must produce an intermediary molecule, the antigenome (a positive RNA strand).

• RNA polymerase, which plays the replicase role, identifies the trailer and binds to the 5' end of the virus genome at the level of the antigenomic promoter. Ignoring attenuating intergenic signals, it makes a complete complementary copy of negative RNA without stopping.

• The positive RNA produced is encapsidated at the same time that it is synthesized.

• The nucleocapsid N-antigenome then serves as a matrix for the synthesis of new negative RNA that also will encapsidate themselves. The latter then can serve as a matrix for the synthesis of new positive RNA, be used for the synthesis of messenger RNA, or associate with neo-structural proteins to form new virions. A regulatory mechanism maintains a ratio of one antigenome for every 10 genomes.

• It is then the turn of the matrix (M) protein to intervene as the band leader in the assembly of new virions. Thanks to its affinity for the N nucleoprotein, it establishes links between the neo-nucleocapsids and the H and F proteins, future spicules of the viral envelope inserted on the cell membrane.