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Activation of the IκB kinase (IKK) is central to NF-κB signaling. However, the precise activation mechanism by which catalytic IKK subunits gain the ability to induce NF-κB transcriptional activity is not well understood. Here we report a 4 Å x-ray crystal structure of human IKK2 (hIKK2) in its catalytically active conformation. The hIKK2 domain architecture closely resembles that of Xenopus IKK2 (xIKK2). However, whereas inactivated xIKK2 displays a closed dimeric structure, hIKK2 dimers adopt open conformations that permit higher order oligomerization within the crystal. Reversible oligomerization of hIKK2 dimers is observed in solution. Mutagenesis confirms that two of the surfaces that mediate oligomerization within the crystal are also critical for the process of hIKK2 activation in cells. We propose that IKK2 dimers transiently associate with one another through these interaction surfaces to promote trans auto-phosphorylation as part of their mechanism of activation. This structure-based model supports recently published structural data that implicate strand exchange as part of a mechanism for IKK2 activation via trans auto-phosphorylation. Moreover, oligomerization through the interfaces identified in this study and subsequent trans auto-phosphorylation account for the rapid amplification of IKK2 phosphorylation observed even in the absence of any upstream kinase.

Although antibodies targeting specific tumor-expressed antigens are the standard of care for some cancers, the identification of cancer-specific targets amenable to antibody binding has remained a bottleneck in development of new therapeutics. To overcome this challenge, we developed a high-throughput platform that allows for the unbiased, simultaneous discovery of antibodies and targets based on phenotypic binding profiles. Applying this platform to ovarian cancer, we identified a wide diversity of cancer targets including receptor tyrosine kinases, adhesion and migration proteins, proteases and proteins regulating angiogenesis in a single round of screening using genomics, flow cytometry, and mass spectrometry. In particular, we identified BCAM as a promising candidate for targeted therapy in high-grade serous ovarian cancers. More generally, this approach provides a rapid and flexible framework to identify cancer targets and antibodies. [ABSTRACT FROM AUTHOR]

: Conformational change in human IKK2 permits dimers to form higher-order oligomers that support interaction between kinase domains and promote activation through trans auto-phosphorylation. [ABSTRACT FROM AUTHOR]

HIV-1 and most of the other lentiviruses encode Vif (virion infectivity factor), an accessory protein that the virus requires to replicate in primary CD4+ T-cells and monocytes. The host cell factor with which Vif interacts was recently identified as APOBEC3G, a cytidine deaminase related to the RNA-editing enzymes. Identification of this key host protein has allowed for dramatic leaps in our understanding of how Vif functions. Vif prevents the encapsidation of APOBEC3G into HIV-1 virions during virus assembly. If not for Vif, the encapsidated APOBEC3G would damage the virus reverse transcripts, causing their degradation and closing the open reading frames of its genes.