2. Coronavirus Properties
Genome: have the largest of RNA virus genomes: 30 kB; may represent the upper limit in size. Perhaps because of the error rate and their size,
coronaviruses undergo high frequency of recombination. Produce a
nested set of mRNAs.
Virion Morphology: nm, enveloped, nucleocapsids are helical, virion is roughly spherical, not icosahedral
Envelope Proteins: Spike protein (S) possesses the receptor binding
activity, the fusion activity and is the major determinant for neutralizing antibodies; Membrane protein (M) is an integral membrane protein
spanning the membrane 3 times; in some coronaviruses there is an
hemaglutinin-esterase (H-E) that is homologous to the influenza C virus H-E
Disease: human coronavirus causes colds and perhaps gastroenteritis; in other animals coronaviruses cause gastroenteritis, hepatitis, and a
syndrome similar to multiple sclerosis of humans; SARS

4. Synthesis of Coronavirus RNAs
Coronaviruses use a combination of leader-primed transcription and replication of subgenomic mRNAs
A leader of ~60 nts can prime the synthesis of subgenomic mRNAs starting at promoters in intergenic regions
Subgenomic mRNAs are capable of independent replication once synthesized
It is unclear whether leader-primed transcription occurs from the plus strand RNA, the minus strand RNA, or both
The relative importance of leader-primed transcription versus independent replication of subgenomic mRNAs may differ in different coronaviruses

5. The Coronavirus Transmissible Gastroenteritis Virus

9. Two Murine Coronavirus Genes Suffice for Viral RNA synthesis

11. Assembled Coronavirus from Complementation of Two Defective
Interfering RNAs