Polyadenylation of Friend murine leukemia virus env‐mRNA is affected by its splicing

As splicing was previously found to be important for increasing Friend murine leukemia virus env‐mRNA stability and translation, we investigated whether splicing of env‐mRNA affected the poly(A) tail length using env expression vectors that yielded unspliced or spliced env‐mRNA. Incomplete polyadenylation was detected in a fraction of the unspliced env‐mRNA products in an env gene‐dependent manner, showing that splicing of Friend murine leukemia virus plays an important role in the efficiency of complete polyadenylation of env‐mRNA. These results suggested that the promotion of complete polyadenylation of env‐mRNA by splicing might partially explain up‐regulation of Env protein expression as a result of splicing.