Ubiquitin binding mediates the NF-kappaB inhibitory potential of ABIN proteins.
Deregulated nuclear factor kappaB (NF-kappaB) activation plays an important role in inflammation and tumorigenesis. ABIN proteins have been characterized as negative regulators of NF-kappaB signaling. However, their mechanism of NF-kappaB inhibition remained unclear. With the help of a yeast two-hybrid screen, we identified ABIN proteins as novel ubiquitin-interacting proteins. The minimal ubiquitin-binding domain (UBD) corresponds to the ABIN homology domain 2 (AHD2) and is highly conserved in ABIN-1, ABIN-2 and ABIN-3. Moreover, this region is also present in NF-kappaB essential modulator/IkappaB kinase gamma (NEMO/IKKgamma) and the NEMO-like protein optineurin, and is therefore termed UBD in ABIN proteins and NEMO (UBAN). Nuclear magnetic resonance studies of the UBAN domain identify it as a novel type of UBD, with the binding surface on ubiquitin being significantly different from the binding surface of other UBDs. ABIN-1 specifically binds ubiquitinated NEMO via a bipartite interaction involving its UBAN and NEMO-binding domain. Mutations in the UBAN domain led to a loss of ubiquitin binding and impaired the NF-kappaB inhibitory potential of ABINs. Taken together, these data illustrate an important role for ubiquitin binding in the negative regulation of NF-kappaB signaling by ABINs and identify UBAN as a novel UBD.
Wagner
S
S
Institute for Biochemistry II, Goethe University Medical School, Frankfurt, Germany.
Carpentier
I
I
Rogov
V
V
Kreike
M
M
Ikeda
F
F
Löhr
F
F
Wu
C-J
CJ
Ashwell
J D
JD
Dötsch
V
V
Dikic
I
I
Beyaert
R
R
D001665:Binding Sites; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D006801:Humans; D016328:NF-kappa B / Q000037:antagonists & inhibitors* / Q000502:physiology; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism*
D004268:DNA-Binding Proteins; D016328:NF-kappa B; C117046:TNIP1 protein, human; D025801:Ubiquitin