Measles virus Replication Outline:

Measles viruscontains negative stranded RNA and is 150-300 nm in diameter. On its surface it has two membrane proteins - Fusion protein and Hemagglutinin. Hemagglutinin binds to the receptor on the host cell membrane. Here only Hemagglutinin is shown, for a more detailed viral structure see the Morbilivirus

After the virus binds to the host membrane, the viral plasma membrane fuses with the host membrane with the help of the Fusion protein. Then ribonucleocapsid is released into the cytoplasm. In the host cell the sequential transcription takes place, viral mRNAs are capped and polyadenylated in the cytoplasm. In this scene only the formation of the viral membrane protein is shown, viral mRNA codes also other proteins, including the nucleoprotein.

When enough nucleoprotein has been formed, starts the replication of the viral genome. Original viral negative stranded RNA is first duplicated into the so called antigenome (=positive stranded RNA). Antigenome then codes for the final viral genomes (negative stranded RNAs).

Morbilivirus budding:

Budding is the stage when newly formed virus exits the host cell. It takes with it a piece of the host cell membrane along with the synthesized viral proteins residing in this patch of the cell membrane. First the viral content (the negative strand viral RNA - protein complex) enters the bud. Then the viral vesicle is pinched off by membrane scission. Host ESCRT (Endosomal Sorting Complex Required for Transport) components are recruited in order to help in this process. ESCRT machinery is normally used by the cell membrane remodeling like vesicle formation.

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