探討ND1對Cullin3-KLHL20接合酶酵素之調控機制

Abstract

The Cullin-RING E3 Ligases (CRLs) control many important cellular processes by using a family of BTB/POZ domain proteins as substrate adaptors. The mechanisms that regulate the action of this family of E3 ligases have not been completely understood. In this thesis, we identified IVNS1ABP (ND1) as an interacting protein of KLHL20, a Cullin3 (Cul3) substrate adaptor previously identified in our laboratory. Similar to KLHL20, ND1 consists of a BTB/POZ domain and six-tandem kelch repeats. Uniquely, ND1 can neither bind to Cul3 nor serve a KLHL20 substrate. Rather, ND1 stabilizes Cul3-KLHL20 E3 ligases substrate PML through decreasing PML ubiquitination level under normoxia or hypoxia condition. Analysis of the underlying molecular mechanism revealed that ND1 perturbs the function of Cul3-KLHL20 E3 ligases by interfering with the KLHL20-PML and KLHL20-Cul3 interaction. Moreover, lost-of-function analysis showed that ND1 knock-down decreases PML protein level and reduces PML ubiquitination, supporting the physiological role of ND1 in KLHL20-dependent PML regulation. In consistent with our findings, ND1 is able to attenuate the blockage effect of KLHL20 on PML-induced growth inhibition. Taken together, our studies identified ND1 as a negative regulator of the Cul3-KLHL20 E3 ligase via its interaction with KLHL20.