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beta-TrCP mediates the signal-induced ubiquitination of IkappaBbeta
1Section of Immunobiology, Department of Molecular Biophysics, Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
We have examined the role of beta-TrCP (beta-transducin repeat-containing protein) in the ubiquitination and degradation of IkappaBbeta, one of the two major IkappaB isoforms in mammalian cells. We demonstrate that beta-TrCP interacts specifically with IkappaBbeta, and such interaction is dependent on prior phosphorylation of IkappaBbeta on serines 19 and 23. Interaction with beta-TrCP is also necessary for ubiquitination of IkappaBbeta upon stimulation of cells, and deletion of the F-box in beta-TrCP abolishes its ability to ubiquitinate IkappaBbeta. Therefore, these results indicate that beta-TrCP plays a critical role in the activation of NF-kappaB by assembling the ubiquitin ligase complex for both phosphorylated IkappaBalpha and IkappaBbeta.
We have examined the role of beta-TrCP (beta-transducin repeat-containing protein) in the ubiquitination and degradation of IkappaBbeta, one of the two major IkappaB isoforms in mammalian cells. We demonstrate that beta-TrCP interacts specifically with IkappaBbeta, and such interaction is dependent on prior phosphorylation of IkappaBbeta on serines 19 and 23. Interaction with beta-TrCP is also necessary for ubiquitination of IkappaBbeta upon stimulation of cells, and deletion of the F-box in beta-TrCP abolishes its ability to ubiquitinate IkappaBbeta. Therefore, these results indicate that beta-TrCP plays a critical role in the activation of NF-kappaB by assembling the ubiquitin ligase complex for both phosphorylated IkappaBalpha and IkappaBbeta.