IDENTIFICATION OF SIGNALS REQUIRED FOR THE INSERTION OF HETEROLOGOUS GENOME SEGMENTS INTO THE REOVIRUS GENOME

In cells simultaneously infected with any tno of the three reovirus se rotypes ST1, ST2, and ST3, up to 15% of the yields are intertypic reas sortants that contain all possible combinations of parental genome seg ments. We have now found that not all genome segments in reassortants are mild type. In reassortants that possess more ST1 than ST3 genome s egments, all ST1 genome segments appear to be mild type, but the incom ing ST3 genome segments possess mutations that make them more similar to the ST1 genome segments that they replace, In reassortants resultin g from crosses of the more distantly related ST3 and ST2 viruses that possess a majority of ST3 genome segments, all incoming ST2 genome seg ments are wild type, but the ST3 S4 genome segment possesses two mutat ions, G74 to A and G624 to A, that function as acceptance signals, Rec ognition of these signals has far-reaching implications for the constr uction of reoviruses with novel properties and functions.