The transcription/replication activity of the polymerase of influenza A viruses is not correlated with the level of proteolysis induced by the PA subunit

The PA subunit of the influenza virus polymerase has been shown to induce d egradation of coexpressed proteins, but its role in the replication activit y of the polymerase is not fully understood. Here, PA proteins derived from several influenza A viruses were examined at 37 and 33 degreesC for both t he level of proteolysis they induced and the efficiency with which they ens ured transcription/replication of a viral-like RNA within a polymerase comp lex reconstituted in vivo from cloned cDNAs. Two mutants of A/Victoria/3/75 PA showed a decreased ability to induce proteolysis as compared to the wil d-type PA, but still appeared to be as active as the wild-type protein with respect to the polymerase activity. Furthermore, we observed that the abil ity of PR8-PA to induce proteolysis was severely impaired at 33 degreesC as compared to 37 degreesC, while the efficiency with which the PR8-derived p olymerase complex ensured transcription/replication of the viral-like RNA w as similar at both temperatures. Taken together, our observations suggest t hat the transcription/replication activity of the polymerase of influenza A viruses is not correlated with the level of proteolysis induced by the PA subunit. (C) 2001 Academic Press.