| Summary: | 碩士 === 國立臺灣大學 === 分子醫學研究所 === 95 === The BTB-kelch protein KLEIP (Kelch-like ECT2 interacting protein) is a 64 kDa protein which contains a BTB/POZ domain, a BACK domain, and six kelch repeats. Previous study in our laboratory identified KLEIP as a binding partner of DAPK (Death -associated protein kinase) and revealed a function of KLEIP as the substrate adaptor of Cul3 ubiquitin E3 ligase complex to promote DAPK ubiquitination and proteasomal degradation. In this thesis, we first found that KLEIP was ubiquitously expressed in various tissues and cell lines and present in detergent insoluble compartment of cells. We also demonstrated the essential roles of endogenous KLEIP and the KLEIP binding ability of Cul3 to promote DAPK ubiquitination, further confirming DAPK as a substrate of KLEIP/Cul3/Roc1 E3 ligase complex. In addition, we explored whether the substrate adaptor KLEIP itself would be modified and/or regulated. Based on the results of yeast two-hybrid screen for putative KLEIP-interacting proteins and sequence analysis of KLEIP protein, we postulated that KLEIP may undergo SUMO modification. Indeed, we demonstrated that KLEIP was sumoylated in vivo, and this modification was up-regulated under hypoxia conditions. Furthermore, we found that KLEIP can bind SUMO1 non-covalently through its consensus SUMO interacting motifs (SIMs). Together, we revealed the post-translational SUMO modification and SUMO1-binding ability of KLEIP, and we speculated that sumoylation and SUMO1-interaction of KLEIP may regulate its function and/or subcellular localization to influence the ubiquitination of DAPK.
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