Abstract: The present invention relates to the discovery, identification and characterization of nucleotides that encode novel substrate-targeting subunits of ubiquitin ligases. The invention encompasses nucleotides encoding novel substrate-targeting subunits of ubiquitin ligases: FBP1, FBP2, FBP3, FBP4, FBP5, FBP6, FBP7, FBP8, FBP9, FBP10, FBP11, FBP12, FBP13, FBP14, FBP15, FBP16, FBP17, FBP18, FBP19, FBP20, FBP21, FBP22, FBP23, FBP24, and FBP25, transgenic mice, knock-out mice, host cell expression systems and proteins encoded by the nucleotides of the present invention.

Abstract: The present invention relates to the discovery and characterization of activity of Fbp1, a substrate-targeting ubiquitin ligase subunit. The invention encompasses interactions between Fbp1 and its substrates, including Fbp5, ?-Catenin, and I?B?. The invention also encompasses interactions between the Fbp1 isoform ?-Trcp2 and its substrates, including Fbp5, b-Catenin, and I?B?. The present invention relates to screening assays that use Fbp1 and/or ?-Trcp2 to identify potential therapeutic agents such as small molecules, compounds or derivatives which modulate Fbp1 and/or ?-Trcp2 activity for the treatment of proliferative and differentiative disorders, including infertility, cancer, major opportunistic infections, immune disorders, certain cardiovascular diseases, and inflammatory disorders. The invention also encompasses methods to diagnose and treat Fbp1-related infertility disorders.