A model for subcellular localization of BCL10 under various conditions. (A) Normal lymphocyte: BCL10 is localized in cytoplasm because nuclear BCL10 is exported by MALT1. (B) t(11;18) MALT lymphoma: Normal MALT1 products are reduced by half because the translocated allele generates API2-MALT1. Since the API2-MALT1 cannot export nuclear BCL10, the reduction of normal MALT1 proteins will be less efficient in BCL10 exportation, resulting in nuclear retention of BCL10. (C) t(1;14) MALT lymphoma: Overexpressed BCL10 results in nuclear retention because of a relative shortage of MALT1.