Identification of novel mediators of NF-B through genome- wide survey of monocyte adherence-induced genes

Abstract: The transcription factor nuclear factor (NF)-B controls the expression of genes involved in inflammation, cell proliferation, apoptosis, and differentiation. Impaired regulation of NF-B has been associated with many diseases; thus, there is significant interest in therapeutic approaches based on modulation of this transcription factor. NF-B activity is controlled by numerous signaling mole-cules, many of which are potentially to be identi-fied. Monocytes are principal effectors of the im-mune system, and monocyte adherence is the first step leading to their activation and differentiation. Adherence induces activation of NF-B, resulting in the induction of proinflammatory genes as well as anti-inflammatory genes, which counterbalance and limit the intensity and duration of NF-B acti-vation. Here, to identify novel mediators of NF-B signaling, we used the model of monocyte adher-ence to perform a systematic, genome-wide survey of adherence-induced genes. Having isolated mRNAs from nonadherent and adherent primary human monocytes, we constructed suppressive subtrac-tion hybridization libraries containing cDNAs, which were differentially regulated by adherence. Of 366 identified differentially expressed genes, most were found to be up-regulated by adherence. Having analyzed a subset of these genes, we found that the library was enriched with inhibitors of NF-B. Three of those (an orphan nuclear recep-tor NUR77, a guanosine 5-diphosphate/guanosine 5-triphosphate exchange factor RABEX5, and a PRK1-associated protein AWP1) were particu-larly potent inhibitors of NF-B activation. Thus, the collection of monocyte adherence-regulated genes represents a rich source for the identifica-tion of novel components of the machinery that controls NF-B activation. J. Leukoc. Biol. 78