Arabidopsis ETA2, an apparent ortholog of the human cullin-interacting protein CAND1, is required for auxin responses mediated by the SCF(TIR1) ubiquitin ligase.
نویسندگان
چکیده
Auxin response in Arabidopsis thaliana requires the SCF(TIR1) ubiquitin ligase. In response to the hormone, SCF(TIR1) targets members of the auxin/indoleacetic acid (Aux/IAA) family of transcriptional regulators for ubiquitin-mediated proteolysis. To identify additional regulators of SCF(TIR1) activity, we conducted a genetic screen to isolate enhancers of the tir1-1 auxin response defect. Here, we report our analysis of the eta2 mutant. Mutations in ETA2 confer several phenotypes consistent with reduced auxin response. ETA2 encodes the Arabidopsis ortholog of human Cullin Associated and Neddylation-Dissociated (CAND1)/TIP120A, a protein recently identified as a cullin-interacting factor. Previous biochemical studies of CAND1 have suggested that it specifically binds to unmodified CUL1 to negatively regulate SCF assembly. By contrast, we find that ETA2 positively regulates SCF(TIR1) because Aux/IAA protein stability is significantly increased in eta2 mutants. Modification of CUL1 by the RUB1/NEDD8 ubiquitin-like protein has been proposed to free CUL1 from CAND1 and promote SCF assembly. We present double mutant analyses of eta2 axr1 plants indicating that liberating CUL1 from ETA2/CAND1 is not the primary role of the RUB modification pathway in the regulation of SCF activity. Our genetic and molecular analysis of SCF(TIR1) function in eta2 mutants provides novel insight into the role of CAND1 in the regulation of SCF ubiquitin-ligase activity.
منابع مشابه
Role of the Arabidopsis RING-H2 protein RBX1 in RUB modification and SCF function.
The ubiquitin-related protein RUB/Nedd8 is conjugated to members of the cullin family of proteins in plants, animals, and fungi. In Arabidopsis, the RUB conjugation pathway consists of a heterodimeric E1 (AXR1-ECR1) and a RUB-E2 called RCE1. The cullin CUL1 is a subunit in SCF-type ubiquitin protein ligases (E3s), including the SCF(TIR1) complex, which is required for response to the plant horm...
متن کامل-Mediated Auxin Response
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The AXR6 gene is required for auxin signaling in the Arabidopsis embryo and during postembryonic development. One of the effects of auxin is to stimulate degradation of the Aux/IAA auxin response proteins through the action of the ubiquitin protein ligase SCF(TIR1). Here we show that AXR6 encodes the SCF subunit CUL1. The axr6 mutations affect the ability of mutant CUL1 to assemble into stable ...
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ورودعنوان ژورنال:
- The Plant cell
دوره 16 7 شماره
صفحات -
تاریخ انتشار 2004