<p>Shows a working model that describes a pathway for viral RNA synthesis in MHV-A59-infected cells. The model proposes that the replicase-transcriptase complex forms initially and creates a negative-strand template. It is then converted to utilize the negative strand as a template for positive-strand synthesis and, finally, the complex is inactivated by the degradation of negative-strand templates. It is also proposed that proteolytic processing of the replicase polyproteins plays a role in regulation of this pathway. Also depicted are the putative defects of specific MHV-A59 <i>ts</i> mutants. It remains to be shown whether or not the group IV and VI mutants (Wü <i>ts</i>38, Alb <i>ts</i>17, Wü <i>ts</i>18, and Wü <i>ts</i>36) are defective in negative-strand RNA synthesis at the non-permissive temperature.</p
