Mapping of a Region of the PA-X Protein of Influenza A Virus That Is Important for Its Shutoff Activity

Influenza A virus PA-X comprises an N-terminal PA endonuclease domain and a C-terminal PA-X-specific domain. PA-X reduces host and viral mRNA accumulation via its endonuclease function. Here, we found that the N-terminal 15 amino acids, particularly six basic amino acids, in the C-terminal PA-X-specific region are important for PA-X shutoff activity. These six basic amino acids enabled a PA deletion mutant to suppress protein expression at a level comparable to that of wild-type PA-X.