Molecular analysis of the envelope gene and long terminal repeat of Friend mink cell focus-inducing virus: implications for the functions of these sequences

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Abstract
The envelope (env) gene and 3'' long terminal repeat of a Friend mink cell focus-inducing virus (F-MCFV) were sequenced. The gp70 coding regions for 2 c[complementary]DNA clones of another F-MCFV were also sequenced. The deduced amino acid sequence of the env gene products of both F-MCFV were compared to the corresponding sequences of other MCFV and of ecotropic viruses. The env polypeptides of the different viruses showed long stretches of homology in the carboxy-terminal half of gp70 and in p15env (constant region). The amino-terminal half of gp70 was very similar in all MCFV but showed extensive variations relative to the ecotropic viruses (differential region). This differential region in all MCFV is of endogeneous origin. Evidently, this region carries determinants for ecotropic or polytropic host range. No indication could be found that the env gene products determine the histological type of disease caused by particular MCFV. When the long terminal repeats of F-MCFV and Friend murine leukemia virus were compared with those of other viruses causing either lymphatic leukemia or erythroleukemia, several nucleotides were localized which might determine the histological type of disease caused by these viruses.