Search for physiological substrates and functional analysis of F-box protein β-TrCP in vivo

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Our purpose of this project is elucidation of the regulation of protein expression on development. We have analyzed the function of F-box proteins β-TrCP2, and demonstrated its role on development and differentiation during embryogenesis.β-TrCP1 is the ubiquitin ligase which ubiquitinates β-catenin and l_<κ>βα The gene-targeted mouse of β-TrCP1, which we have generated, still exhibited degradation of β-catenin and l_<κ>βα, suggesting existence of other ubiquitin ligases for β-catenin and l_<κ>βα.The gene-targeted mouse of β-TrCP2, the homologue of β-TrCP1 is embryonic lethal at embryonic day9.5. This difference of phenotype between β-TrCP1 knockout mouse and that of β-TrCP2, indicate that each proteins have different biological functions significantly, even though the difference of biochemical functions have not been reported.We analyzed four proteins picked up based on the expression during early and middle embryogenesis and the consensus sequences, which are recognized by β-TrCP2. However, we did not detected bindings between these proteins and β-TrCP2, and ubiquitination and degradation by β-TrCP2.We have generated β-TrCP2 conditional knockout mouse.B-TrCP1 knockout primary embryonic fibroblasts have shown the abnormal regulation of Period 2 protein expression, suggesting that maintenance of circadian rhythm requires protein degradation by β-TrCP1.