The conserved RING-H2 finger of ROC1 is required for ubiquitin ligation.

ROC1 is a common component of a large family of ubiquitin E3 ligases that regulate cell cycle progression and signal transduction pathways. Here we present evidence suggesting that a conserved RING-H2 structure within ROC1 is critical for its ubiquitin ligation function. Mercury-containing sulfhydryl modification agents (rho-hydroxymercuribenzoate and mercuric chloride) irreversibly ...
inhibit the ROC1-CUL1 ubiquitin ligase activity without disrupting the complex. Consistent with this, these reagents also eliminate the ability of the Skp1-CUL1-HOS-ROC1 E3 ligase complex to support the ubiquitination of IkappaBalpha. Site-directed mutagenesis analysis identifies RING-H2 finger residues Cys(42), Cys(45), Cys(75), His(77), His(80), Cys(83), Cys(94), and Asp(97) as being essential for the ROC1-dependent ubiquitin ligase activity. Furthermore, C42S/C45S and H80A mutations reduce the ability of ROC1 to interact with CUL1 in transfected cells and diminish the capacity of ROC1-CUL1 to form a stable complex with Cdc34 in vitro. However, C75S, H77A, C94S, and D97A substitutions have no detectable effect on ROC1 binding activities. Thus, the ROC1 RING-H2 finger may possess multiple biochemical properties that include stabilizing an interaction with CUL1 and recruiting Cdc34. A possible role of the RING finger in facilitating the Ub transfer reaction is discussed.
Mesh Terms:
Amino Acid Sequence, Amino Acid Substitution, Animals, Binding Sites, Cell Line, Conserved Sequence, Cysteine, Humans, Hydroxymercuribenzoates, Kinetics, Ligases, Mercuric Chloride, Mice, Mutagenesis, Site-Directed, Protein Conformation, Recombinant Fusion Proteins, Sulfhydryl Reagents, Transfection, Ubiquitin-Protein Ligase Complexes, Ubiquitin-Protein Ligases, Ubiquitins
J. Biol. Chem.
Date: May. 19, 2000
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