RNA-Seq and ChIP-Seq reveals SQSTM1/p62 as a key mediator of JunB suppression of NF-κB-dependent inflammation

Mice with epidermal deletion of JunB transcription factor displayed a psoriasis-like inflammation. The relevance of these findings to humans and the mechanisms mediating JunB function are not fully understood. Here, we demonstrate that impaired JunB function via gene silencing or overexpression of a dominant negative mutant increased human keratinocyte cell proliferation but decreased cell barrier function. RNA-seq revealed over 500 genes affected by JunB loss-of-function which included an upregulation of an array of proinflammatory molecules relevant to psoriasis. Among these were TNFα, CCL2, CXCL10, IL6R and SQSTM1, an adaptor protein involved in NF-κB activation. ChIP-Seq and gene reporter analyses showed that JunB directly suppressed SQSTM1 through binding to a consensus AP-1 cis-element located around 2 Kb upstream of SQSTM1-trasncription start site. Similar to JunB loss-of-function, SQSTM1-overexpression induced TNFα, CCL2 and CXCL10. Conversely, NF-κB-inhibition genetically with a mutant IκBα or pharmacologically with PDTC prevented cytokine, but not IL6R, induction by JunB-deficiency. Taken together, our findings indicate that JunB controls epidermal growth, barrier formation and proinflammatory responses through direct and indirect mechanisms, pinpointing SQSTM1 as a key mediator of JunB-suppression of NF-κB-dependent inflammation.