MTREX and AL amyloidosis: To further evaluate the impact that the modeled multiple myeloma amino acid substitution may have on the RNA exosome-Mtr4 interaction in vivo, we tested whether the rrp4-M68T variant exhibits genetic interactions with mpp6 or rrp47 mutants by deleting these non-essential, nuclear exosome cofactor genes MPP6 and RRP47 in combination with rrp4-M68T.