SMN1 and infection: Infection of cultured cells with poliovirus results in the specific cleavage of Gemin3 by a virus-encoded proteinase (Almstead and Sarnow, 2007) and activation of the calcium-dependent protease calpain, mediates Gemin3 and SMN proteolysis (Walker et al., 2008; de la Fuente et al., 2018).