The genomes of three coronaviruses

Abstract

A number of studies on the genomic RNAs of coronaviruses have been reported. The genome of avian infectious bronchitis virus (IBV) is a single single-stranded molecule of high mol. wt [l-4] , which is prone to degradation into smaller molecules [ 1,5] . There is some disagreement concerning its mol. wt with estimates varying from 9.0 X lo6 [l] to 5.6 X lo6 [4]. Similar studies on the human coronavirus (HCV) genome have also shown it to be a large molecule of mol. wt varying from 6.1 X lo6 for strain OC43 [6] to 5.8 X IO6 for strain 2298 [7]. Again, as with IBV, the HCV genome is prone to degradation [6,7]. The genomes of two porcine coronaviruses, transmissible gastroenteritis virus (TGEV) and haemagglutinating encephalomyelitis virus (HEV), have also been shown to be large single single-stranded RNA molecules of about 60 S that dissociate into 35 S and 4 S material on heating above 60°C [8] ~ Coronavirus genomes possess certain mRNA characteristics. Polyadenylic acid [poly(A)] sequences are found in the genomes of IBV [2,4,9] and HCV [7,10] at or near their 3’-termini [7] . Furthermore, the genome of IBV has been shown to be infectious [4,9] and no detectable virion transcriptase has been identified associated with IBV [4] or HCV [lo] particles. In this paper, studies on the characteristics of the genomes of HCV strain 229E (HCV 229E) and IBV strain Beaudette (IBV Beau) reported in [3,7] are extended, and the structure of the genome of another coronavirus, mouse hepatitis virus strain 3 (MHV 3) is analysed for the first time. A comparison of the results shows a much greater similarity between coronavirus genomes than has been previously observed.