NS5 : the presence of this 105 kDa protein results in inactivation of STAT2 (via the signal transduction of the response to interferon) when it is expressed alone.[23] When NS5 is cleaved with NS4B by a protease (NS2B3) it can degrade STAT2. In fact, after the cleavage of NS5 by the protease, there is an E3 ligase association with STAT2, and the E3 ligase targets STAT2 for the degradation