Interactions of the COP9 Signalosome with the E3 Ubiquitin Ligase SCF^(TIR1) in Mediating Auxin Response

Abstract

The COP9 signalosome is an evolutionary conserved multiprotein complex of unknown function that acts as a negative regulator of photomorphogenic seedling development in Arabidopsis. Here, we show that plants with reduced COP9 signalosome levels had decreased auxin response similar to loss-of-function mutants of the E3 ubiquitin ligase SCF^(TIR1). Furthermore, we found that the COP9 signalosome and SCF^(TIR1) interacted in vivo and that the COP9 signalosome was required for efficient degradation of PSIAA6, a candidate substrate of SCF^(TIR1). Thus, the COP9 signalosome may play an important role in mediating E3 ubiquitin ligase–mediated responses.

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