Abstract
The nucleoprotein-encoding gene (N) of murine hepatitis virus type 3 (MHV 3), from the Mill Hill strain, was cloned and sequenced. It was compared to gene N from other murine coronaviruses and was found to share more similarities with N sequences from MHV 1 and MHV JHM strains than with the published MHV 3 N sequence which is almost identical to MHV A59. We suggest that the evolution of some MHV N sequences resulted from a double recombination phenomenon between two ancestors. Furthermore, comparison of protein N from avian and mammalian coronaviruses leads to the hypothesis that horizontal transfer events of the virus from one host species to another have occurred.