ABSTRACT
FLAVIVIRUS STRUCTURE AND REPLICATION Flavivirions are spherical particles approximately 50 nm in diameter, the structure of which has been defined in detail with X-ray crystallography and cryoelectron microscopy (1) (Fig. 1A). The genome is a single-stranded RNA molecule of positive polarity of about 11,000 nucleotides (nt) in length. It contains a long open reading frame (ORF) flanked by 50 and 30
untranslated terminal regions (UTRs), approximately 120 and 500 nt in length, respectively. The ORF encodes a polyprotein precursor that is cleaved co-and posttranslationally, resulting in individual viral proteins. The virus proteins are encoded in the order: C-prM/M-E-NS1-NS2A/2B-NS3-NS4A/4B-NS5, where C (core), prM/M (pre-membrane/membrane), and E (envelope) are the structural proteins, that is, the components of viral particles, and NS are the nonstructural proteins functioning in intracellular virus replication (Fig. 1B).
