| Summary: | 碩士 === 國立臺灣大學 === 分子醫學研究所 === 94 === The specificity of ubiquitination as well as the subsequent protein degradation is controlled by the substrate-specific adaptors that recruit substrates to the core ubiquitin ligase (E3) complexes. In Drosophila, it is known that the Hedgehog (Hh) pathway effector, Cubitus interruptus (Ci), is targeted by the adaptor protein Roadkill (Rdx) to Cullin3 (Cul3)-based E3 for ubiquitination. However, the existence of additional adaptor proteins is suggested by the less extent of Ci accumulation in the rdx mutant cells compared to that of Cul3 mutants. Besides, the Ci subcellular localization change in the Cul3 mutant cells implies that Cul3 regulates Hh pathway in multiple aspects. Here, I identified a potential adaptor protein, BtbVII, which binds Cul3 in vitro and in vivo. In a yeast two-hybrid database PIMRider, BtbVII has been shown to interact with two Hh pathway components Ci and Costal2 (Cos2), which liberates Ci to the nucleus in response to high Hh signals. We have confirmed the binding of BtbVII to Cos2 by means of GST pull-down. Moreover, Cos2 and Ci protein levels are reduced in the BtbVII overexpressing cells. Hence BtbVII is likely the linker that recruits Cos2 to Cul3 for ubiquitination; it may explain the Cul3-mediated control of Ci nuclear translocation. Taken together, I demonstrate that BtbVII is a potential substrate-specific adaptor for Cul3-based ubiquitin ligases, and it may regulate Hh signaling pathway by targeting Cos2 and Ci for ubiquitination.
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