BIK and infection: To determine whether the expression of β5 was affected by IAV infection or viral NP expression we reprobed membranes and found that both infection with IAV (Fig. 5A) and overexpression of viral NP (Fig. 5C) inhibited β5 expression, suggesting that IAV-NP inhibits degradation of ubiquitin-conjugated BIK by the catalytic subunit of the 20S proteasome.