Given the intimate link between inflammation and dysregulated cell proliferation in cancer, we investigated cytokine-triggered gene expression in different cell cycle stages. Transcriptome analysis revealed that G1 release through cyclin-dependent kinase 6 (CDK6) and CDK4 primes and cooperates with the cytokine-driven gene response. CDK6 physically and functionally interacts with the NF-κB subunit p65 in the nucleus and is found at promoters of many transcriptionally active NF-κB target genes. CDK6 recruitment to distinct chromatin regions of inflammatory genes was essential for proper loading of p65 to its cognate binding sites and for the function of p65 coactivators, such as TRIP6. Furthermore, cytokine-inducible nuclear translocation and chromatin association of CDK6 depends on the kinase activity of TAK1 and p38. These results have widespread biological implications, as aberrant CDK6 expression or activation that is frequently observed in human tumors modulates NF-κB to shape the cytokine and chemokine repertoires in chronic inflammation and cancer.

Histone deacetylase (HDAC) 3, as a cofactor in co-repressor complexes containing silencing mediator for retinoid or thyroid-hormone receptors (SMRT) and nuclear receptor co-repressor (N-CoR), has been shown to repress gene transcription in a variety of contexts. Here, we reveal a novel role for HDAC3 as a positive regulator of IL-1-induced gene expression. Various experimental approaches involving RNAi-mediated knockdown, conditional gene deletion or small molecule inhibitors indicate a positive role of HDAC3 for transcription of the majority of IL-1-induced human or murine genes. This effect was independent from the gene regulatory effects mediated by the broad-spectrum HDAC inhibitor trichostatin A (TSA) and thus suggests IL-1-specific functions for HDAC3. The stimulatory function of HDAC3 for inflammatory gene expression involves a mechanism that uses binding to NF-κB p65 and its deacetylation at various lysines. NF-κB p65-deficient cells stably reconstituted to express acetylation mimicking forms of p65 (p65 K/Q) had largely lost their potential to stimulate IL-1-triggered gene expression, implying that the co-activating property of HDAC3 involves the removal of inhibitory NF-κB p65 acetylations at K122, 123, 314 and 315. These data describe a novel function for HDAC3 as a co-activator in inflammatory signaling pathways and help to explain the anti-inflammatory effects frequently observed for HDAC inhibitors in (pre)clinical use.