POSH2 is a RING finger E3 ligase with Rac1 binding activity through a partial CRIB domain

Abstract The Plenty of SH3 domains protein (POSH) is an E3 ligase and a scaffold in the JNK mediated apoptosis, linking Rac1 to downstream components. We here describe POSH2 which was identified from a p21-activated kinase 2 (PAK2) interactor screen. POSH2 is highly homologous with other members of the POSH family; it contains four Src homology 3 (SH3) domains and a RING finger domain which confers E3 ligase activity to the protein. In addition POSH2 contains an N-terminal extension which is conserved among its mammalian counterparts. POSH2 interacts with GTP-loaded Rac1. We have mapped this interaction to a previously unrecognized partial Cdc42/Rac1-interactive binding domain. Structured summary MINT- 7987761 : POSH1 (uniprotkb: Q9HAM2 ) physically interacts (MI: 0915 ) with Ubiquitin (uniprotkb: P62988 ) by anti tag coimmunoprecipitation (MI: 0007 ) MINT- 7987932 : PAK2 (uniprotkb: Q13177 ) binds (MI: 0407 ) to CDC42 (uniprotkb: Q07912 ) by solid phase assay (MI: 0892 ) MINT- 7987908 : POSH1 (uniprotkb: Q9HAM2 ) binds (MI: 0407 ) to Rac1 (uniprotkb: P63000 ) by solid phase assay (MI: 0892 ) MINT- 7987880 : POSH2 (uniprotkb: Q8TEJ3 ) binds (MI: 0407 ) to Rac1 (uniprotkb: P63000 ) by solid phase assay (MI: 0892 ) MINT- 7987734 : POSH2 (uniprotkb: Q8TEJ3 ) physically interacts (MI: 0915 ) with Ubiquitin (uniprotkb: P62988 ) by anti tag coimmunoprecipitation (MI: 0007 ) MINT- 7987779 , MINT- 7987804 , MINT- 7987824 , MINT- 7987838 , MINT- 7987853 : Rac1 (uniprotkb: P63000 ) physically interacts (MI: 0915 ) with POSH2 (uniprotkb: Q8TEJ3 ) by anti tag coimmunoprecipitation (MI: 0007 ) MINT- 7987920 : PAK2 (uniprotkb: Q13177 ) binds (MI: 0407 ) to Rac1 (uniprotkb: P63000 ) by solid phase assay (MI: 0892 )