Deletions at the C-terminus of interferon gamma reduce RNA binding and activation of double-stranded-RNA cleavage by bovine seminal ribonuclease.

Recombinant interferon gamma (IFN-gamma) from three species activates the cleavage of double stranded (ds-) RNA by the dimeric RNAase isolated from bovine semen (BS-RNAase). Human and bovine IFN-gamma bind RNA tightly enough to inhibit cleavage by RNAase A [Schein, Haugg and Benner (1990) FEBS Lett. 270, 229-232]. Murine IFN-gamma and a proteolytic fragment of human IFN-gamma, both of which lack part of the positively charged C-terminus, bind RNA weakly and do not inhibit RNAase A. Their ability to activate BS-RNAase is proportional to their activity in the anti-viral assay. Two monoclonal antibodies that neutralize the anti-viral activity of human IFN-gamma inhibit the activation of BS-RNAase by both full-length and proteolysed human IFN-gamma. Our results demonstrate that the C-terminus of IFN-gamma contributes to RNA binding and activation of BS-RNAase, as well as to anti-viral activity.