TOB1: ProductsTransducer of ERBB2, 1 (TOB1), also known as TOB, is a 345 amino acid (aa) member of the BTG/TOB family of proteins with a predicted molecular weight of 38 kDa. The members of this protein family are characterized by a B Cell Translocation Gene (BTG) homology domain. Human TOB1 shares 96% aa sequence identity with the mouse and rat orthologs. TOB1 has antiproliferative activity that is at least partially mediated by its ability to promote mRNA deadenylation and negatively regulate Cyclin D1 expression. It localizes to both the nucleus and the cytoplasm, but only its nuclear localization appears to be important for its ability to inhibit cell proliferation. TOB1 is regulated post-translationally via both ubiquitination and phosphorylation. The Ubiquitin ligases SCFSkp2, CRN7, and Cul4-DDB1Cdt2 have all been reported to ubiquitinate TOB1 and promote its degradation via the 26S Proteasome. However, phosphorylation of TOB1 by Cdc7 prevents its Cul4-DDB1Cdt2-dependent degradation. Additionally, TOB1 is inhibited by ERK1/ERK2-dependent phosphorylation. In accordance with its antiproliferative activity, TOB1 has been shown to suppress both gastric and breast cancer.